Interlayer Adhesion Analysis of 3D-Printed Continuous Carbon Fibre-Reinforced Composites

Carbon fibre-reinforced materials are becoming more and more popular in various fields of industries because of their lightweight and perfect mechanical properties. Additive manufacturing technologies can be used for the production of complex parts from various materials including composites. Fused deposition modelling (FDM) is an excellent technology for the production of composite structures reinforced with short or continuous carbon fibre. In this study, modified FDM technology was used for the production of composites reinforced with continuous carbon fibre. The main aim of this study is to evaluate the shear strength of 3D-printed composite structures. The influence of printing layer height and line width on shear strength was analysed. Results showed that layer height has a significant influence on shear strength, while the influence of printing line width on shear strength is slightly smaller. Reduction of layer height from 0.4 mm to 0.3 mm allows increasing shear strength by about 40 percent. Moreover, the influence of the shear area and overlap length on shear force showed linear dependency, in which the shear area is increasing the shear force increasing proportionally. Finally, the results obtained can be used for the design and development of new 3D-printed composite structures.

COMPARISON OF ANALYSIS BETWEEN RECTANGULAR AND CIRCULAR OVERHEAD WATER TANK

Water tank is a container used for the storing of liquids and they are classified based on shape and location. The overhead tank is an important and it is very common public utility structure. The study predicts the analysis and design of the rectangular and circular overhead water tank using ETABS software. The water tank is modeled and analyzed by using dynamic analysis to resist lateral loads and design is made using working stress method manually. Dead load, live load, wind load and seismic loads are applied based on IS codes. The behavior of structure for the parameters like Story drift, displacement, stiffness, deflection, storey shear, base shear, area of steel and hoop tension for circular and rectangular water tank are studied and then comparison of the results is made between circular and rectangular overhead water tank. By this study we say that the circular water tank is suitable for larger capacity and rectangular is suitable for smaller capacity and it is economical for larger capacity.

Brittle Crack Arrestability and Inverse Fracture in DWTT

The drop-weight tear test (DWTT) has been widely used to evaluate the resistance of linepipe steels against brittle crack propagation, and the shear area fraction SA% in the DWTT has been adopted in the requirement for the linepipe steels. However, recent studies have pointed out the issue of ambiguity in evaluation of the DWTT when a ductile crack initiates from the notch and then transits to a brittle crack during ductile crack propagation. This fracture behavior is termed “inverse fracture.” According to the API Recommended Practice 5L3 (API RP 5L3), a test is considered invalid when a DWTT specimen shows inverse fracture. In this case, it is difficult to examine the acceptance criterion (85% shear area transition temperature) for linepipe steels. Because the purpose of the DWTT is to evaluate the brittle crack arrestability of the steels in a pressurized linepipe, the DWTT results should be examined with a propagating brittle crack arrest test. A large-scale brittle crack arrest test called the West Jefferson test is generally conducted to reproduce the crack propagation and arrest behavior in actual linepipes. However, it is somewhat difficult to control the lower test temperature and to initiate brittle crack in recent high-toughness steels in this burst test. Although the test stress conditions of the uniaxial tension in the plate tension brittle crack arrest test and the biaxial tension in a pressurized pipe are different, the plate tension brittle crack arrest test has the advantages of accurate control of the test temperature, test stress, and brittle crack initiation in comparison with the actual pipe burst test. Therefore, in this study, the brittle crack arrestability of linepipe steel which showed inverse fracture in the DWTT was investigated by conducting plate tension brittle crack arrest tests under an isothermal condition (crack arrest temperature test (CAT test)), which simulates the condition of the actual pipelines in service. This study also investigated the local shear lip thickness fraction in the CAT tests together with the shear area fraction SA% measured in DWTTs. Based on the results, the effect of brittle crack arrestability on inverse fracture appearance in the DWTTs was discussed in comparison with the brittle crack arrest behavior in the CAT tests.

THE IMPACT OF SHEAR GAP SIZE ON THE QUALITY OF THE SHEARED SURFACE IN ELECTRICAL STEEL SHEET BLANKING

The quality of the sheared surface when blanking, also known as die-cutting, is the result of several factors. Based on current knowledge about blanking, the following technological parameters – shear gap size, blunting of the shearing tool, lubrication in the shearing process, and deformation rate – can be considered as decisive parameters on the quality of the sheared surface. The main material characteristics include yield strength, tensile strength, ductility, and ferrite grain size. The paper is focused on the influence of the shear gap on the quality of the shear surface of electrical sheets with different chemical composition and different mechanical properties. The quality of the cutting surface was characterized by the size of the plastic cutting area. The relationships between the size of the shear gap, which ranged from 1 to 7% of the thickness of the cut material and the size of the plastic shear area, were evaluated and measured macroscopically.

Strut Confinement of Simply Supports Deep Beam Using Strut Reinforcement

This study investigates the effect of confining the Strut region of the deep beam by using Struts Reinforcement; which consists of four main bars enclosed by stirrups. Six specimens were tested for investigating the behavior of deep beams including; ultimate load, mid-span deflection, crack pattern, first shear and first flexure cracks, concrete surface strain and mode of failure. The specimens were tested under two symmetrical points load with and of 1 and compressive strength of 38 MPa. The main parameters were: first one the diameter of the main bars of Strut Reinforcement (8, 10, 12 mm) with constant spacing of stirrups equal to 80 while the other parameter was varied spacing of stirrups of strut reinforcement (120, 100, and 80 mm) with constant main bars diameter of 8 mm. The test results showed that the Strut confinement generally increased the ultimate load from 750 kN to 1250 kN and the ductility of the beam, confined shear cracks and strain surface across the strut and shear area and turned failures mode from shear failure to flexure. The increase in the diameter of the main bars enhanced the behavior of the beam more than the stirrups number.

Improving the method for determining the granular media strength performance by oblique shear test

To ensure the strength performance of the pavement of open pit truck roads, it is necessary that it conforms not only to the designed required deformation (elasticity) modulus, but also to the condition for ensuring the shear resistance of structural layers made from non-cohesive and lowly cohesive granular media. However, today there are no reliable methods for determining the strength performance of coarse-grained materials, therefore, for them there are no designstrength values, and therefore their shear resistance is not evaluated, which is a serious omission. It is proposed to evaluate the strength performance of granular media by the oblique sheartest, for which an improved design of oblique shear apparatus was developed, which made it possible to adjust the granular medium density (structure) to the corresponding density (structure) under construction conditions. An analysis was also made of the influence of the angle of inclination of the shear area on the predicted values of normal and shear stresses arising in the cross section, which made it possible to establish the recommended values of this indicator depending on the prevailing particle size of the test medium.

SHEAR STRENGTHENING OF REINFORCED CONCRETE BEAM USING EXTERNALLY STRIRRUPS

Initial design errors, especially the installation of stirrups, one of them can cause the beam having shear failure due to installing capacity of stirrups less than the shear capacity that occurs. Shear strengthening in this study used externally stirrups ∅6-75 which were installed in the shear area only. The results of calculation analysis, shear capacity can increase up to 137.82%; 133.42% and 137.12% while the test results increased by 31.58%; 0% and 4.76% in this caseload did not look significant from the results of calculation analysis. However, when viewed from crack pattern that occurs without external stirrups, outer ring has a combination of flexural and shear cracks occurs quite much, besides of flexural and shear cracks, combination of crack also occurs because of pressure beam reach pressure capacity first rather than tensile beam because the ratio of installed reinforcement is over reinforced. Meanwhile, in the beam with external stirrups, the crack pattern that occurs is also a combination of bending and shear cracks, but the cracks that occur are relatively less than the beam without external stirrups. When viewed from the deflection that occurred during the first crack, the reinforced beam experienced a relatively smaller deflection of 0.61 mm beam; 0.31 mm and 0.18 mm rather than beams without externally stirrups 1.28 mm; 0.55 mm and 0.32 mm, so that the beam with external stirrups can be said to be more rigid than the beam without external stirrups. Kesalahan desain awal, khususnya pemasangan sengkang, salah satunya dapat mengakibatkan balok mengalami kegagalan geser akibat kapasitas sengkang yang terpasang kurang dari kapasitas geser yang terjadi. Perkuatan geser pada penelitian ini menggunakan sengkang ∅6-75 yang dipasang pada daerah geser saja. Hasil dari perhitungan analisis, kapasitas geser dapat meningkat sampai 137,82%; 133,42% dan 137,12% sedangkan dari hasil pengujian mengalami peningkatan sebesar 31,58%; 0% dan 4,76% dalam hal ini peningkatan beban tidak terlihat sesignifikan dari hasil analisis perhitungan, namun jika dilihat dari pola retak yang terjadi beton tanpa perkuatan sengkang luar mengalami kombinasi retak lentur dan geser yang cukup banyak, selain kombinasi retak lentur dan geser, juga terjadi retak akibat balok tekan yang mencapai kapasitas tekan terlebih dahulu daripada balok tarik karena rasio tulangan yang terpasang over reinforced. Sementara itu pada balok dengan perkuatan sengkang luar, pola retak yang terjadi juga kombinasi retak lentur dan retak geser, namun retak yang terjadi relatif lebih sedikit daripada balok tanpa perkuatan. Jika ditinjau dari lendutan yang terjadi pada saat crack pertama, balok yang diberi perkuatan mengalami lendutan yang relatif lebih kecil yaitu 0,61 mm; 0,31 mm dan 0,18 mm daripada balok tanpa perkuatan 1,28 mm; 0,55 mm dan 0,32 mm sehingga balok yang diperkuat dengan sengkang luar dapat dikatakan lebih kaku daripada balok tanpa perkuatan.

Influence of different filler weld wire chemistries on metallurgical and mechanical behavior of ultrahigh strength steel welded joints

Three different filler combinations comprising of ferritic, austenitic, and (ferritic + austenitic) were used to fabricate butt welded joints on 15 mm thick ultrahigh strength steel using hybrid arc welding processes. Owing to different weld metal compositions, a significant variation in metallurgical properties of these welds was observed, which consequently affected their mechanical properties in terms of tensile and impact toughness. Acicular ferrite with relatively soft zones formed in the ferritic weld metal imparted better impact toughness and ductility, whereas the joints welded using austenitic filler wire due to formation of hard martensitic structure showed high hardness across all their zones which resulted into higher tensile strength but poor ductility and impact toughness. SEM fractographs facilitated studying of shear lip formation and percentage shear area, and could be correlated with the ductility and impact toughness of the welded joints to a reasonable extent. Among all the welds, ferritic filler showed relatively less joint efficiency as well as ultimate tensile strength, but could be considered as a better choice over the austenitic as well their combination (ferritic + austenitic), as it performed better in terms of tensile ductility as well as impact toughness.

Evaluation of a multi-drum magnetorheological brake via finite element analysis considering number of drums and fluid gap selection in optimization

Under the same excitation, the multi-drum magnetorheological brake has a nonuniform distribution of flux density over fluid gaps. Each fluid gap has its own flux density and shear area. Therefore, the number of drums and the fluid gap selection in optimization are two important parameters to be considered in a multi-drum brake design. When a fluid gap is selected in optimization, the brake is optimized to reach the maximum required flux density over this gap. This article focuses on evaluating the influence of these two parameters on the performance of the multi-drum brake. According to the number of drums and the fluid gap selection in optimization, the brakes were marked and optimized via finite element analysis. After all optimal designs were obtained, the performance in terms of torque, volume, mass, and power consumption as well as the torque–volume, torque–mass, and torque–power ratios were calculated and compared. Based on the evaluation results, suggestions on the number of drums and the fluid gap selection in optimization are given.

Understanding Inverse Fracture: A Comparison of Results of Drop Weight Tear Tests and Partial Gas Tests

For a safe operation of gas pipelines, the prevention of propagating brittle facture is one of the most important requirements. To evaluate the transition temperature of a propagating fracture, the Drop Weight Tear (DWT) Test was developed in the 60s. Fracture surfaces of DWT specimens have been shown to correspond well to the fracture surface of a pipe exposed to a propagating fracture at a certain temperature. Historically, there have always been observations of the fracture initiating in a ductile manner in the DWT test. Nevertheless, the most widely used test standard rules out such behavior, known as inverse or abnormal fracture. As an option to prevent ductile initiation, an alternative notch is proposed. While this might have served in the earlier days, high toughness steels of today are known to provide a high resistance against crack initiation and are therefore prone to inverse fracture, even when making use of the suggested alternative notch. Other, non-standard notch types have been investigated and discussed in literature, amongst these the static pre-crack and brittle weld notch. Observations of the DWT test, especially comparing material showing non-inverse and inverse behaviour, show delayed crack initiation resulting in large deflection when the specimens are inverse. This high degree of pre-deformation of the material will have an adverse influence on the material performance by the time the crack propagates into it. This implies that the appearance of inverse fracture is a test effect in the laboratory test, and not an inherent material property, leading to the question if such DWT test results still correspond to the behavior of pipes. If the correlation is shown to be valid, the brittle initiation requirement as such becomes questionable. This study summarises investigations of different notch types in DWT tests. West Jefferson tests that have been conducted to verify the correlation to shear area fraction in DWT tests. The investigation revealed that ductile initiation could not be reliably suppressed. While neither Chevron nor static pre-crack specimen lead to any reduction of the occurrence of inverse fracture, test series of brittle weld specimens did have a higher number of valid specimens. Interestingly, the results of valid, non-inverse specimens and invalid, inverse specimens showed no shift in transitional behavior. Correspondingly, both valid and invalid specimens showed a good representation of the pipe behaviour in the upper transition region.