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Creep age forming (CAF) is an advanced forming technology that combines creep deformation and age hardening processes. When compared with the conventional forming technologies including roll bending and shot-peen forming, CAF has many advantages of low residual stress, excellent dimensional stability, good service performance and short production cycle. It is an optimal technique for precise manufacturing for shape and properties of large-scale complicated thin-walled components of light-weight and high strength aluminum alloys in the aviation and aerospace industries. Nevertheless, CAF has an inevitable disadvantage that a large amount of springback occurs after unloading, which brings a challenge on the accurate shape forming and property tailoring of components. Therefore, how to achieve accurate prediction and control of springback has always been a bottleneck hindering the development of CAF to more industrial applications. After the factors of affecting springback and measures of reducing springback are summarized from the internal and external aspects, constitutive models for predicting springback and springback compensation methods for CAF of aluminum alloy panel components are reviewed. Then, a review of research progresses on tool design for CAF is presented. Finally, in view of the key issue that it is difficult to predict and control the shape and properties of components during CAF, the technical challenges are discussed and future development trends of CAF are prospected.

As members of Project Team SC4.T5, the authors of this paper present the main outcomes from the work that are intended for implementation within EN 1994-1-1 (Eurocode 4). General design and application rules for shallow floor beams will be presented, with a particular focus on: the classification of the composite cross-section; non-linear bending resistance; and the introduction of transverse bars as shear connectors.

Robotic grasping has become increasingly important in many application areas such as industrial manufacturing and logistics. Because of the diversity and uncertainty of objects and environments, common grippers with one single grasping mode face difficulties to fulfill all the tasks. Hence, we proposed a soft gripper with multiple grasping modes in this study. The gripper consists of four modular soft fingers integrated with layer jamming structure and tendon-driven mechanism. Each finger's rotating shaft of the base uses a torsional spring to decouple the bending deformation and relative rotation. An octopus-mimicking vacuum sucker is installed in the fingertip to generate suction. The effectiveness of the bending deformation and variable stiffness of the design were proved by finite element simulation. Thus, the control model of the finger was built, and the control strategy of multimode grasping of the gripper was proposed. Three control modes were designed to realize the four anthropomorphic grasping modes, including wrap, pinch, hook, and suck. Furthermore, the grasping performance was evaluated to show the abilities. The experiments indicated the superior performance of the proposed gripper and the multimode grasping ability that satisfies various grasping tasks.

Additive manufacturing using carbon-fiber-reinforced plastics (CFRP-AM) allows for fabricating machine parts that are lightweight with high strength and high stiffness. Here, continuous carbon fibers inside a base structure improve the strength and stiffness in the fiber direction. For CFRP-AM fabrication, it is important to design the structure with some consideration of the carbon fiber arrangement. This study aimed to propose a design optimization method for CFRP-AM. The target structure is a two-dimensional infill pattern structure that is lightweight, has a low volume, and easily fabricated using CFRP-AM. To optimize the infill structure and the carbon fiber arrangement, we represented the structure as a geometric graph and discretized for restraining computational costs. We encoded these aspects into a chromosome composed of binary genes considering a continuity of carbon fibers and optimized them using a genetic algorithm. To explain the proposed method's effect, we conducted case studies using a cantilever beam. The first involved optimizing the carbon fiber arrangement to reinforce the structure with less fiber and reduce material costs. The second involved simultaneously optimizing the infill structure and the carbon fiber arrangement to reduce both the base materials and the carbon fiber while retaining the high strength. Following this, we applied the proposed method to optimizing a 3-point bending structure. In addition, the proposed method was applied to designing a bicycle brake lever and the optimized structures were fabricated with CFRP-AM. The results confirmed that the proposed optimization method would be useful in the area of CFRP-AM fabrication.

The friction stir welding and its weld properties such as tensile, micro structure of weld, grain size, and fine mixture of two alloys at to joint using testing methods. To determine the weld quality and conclude properties such as weld quality, weld strength, maximum stress that weld can withstand during operation conditions. There are various processes that involve testing the welded joint from which many are the destructive ones that are used to find the tensile strength, hardness of the joint, bending test and other tests. This paper gives an overview on how important is the fine mixture of the samples that undergo friction stir welding and how it impacts the welded sample properties. Friction stir welding creates more opportunities that are related in understanding the quality of the joint such as testing methods to increase the production by faster analysis of defects. This testing method effectively utilizes that modern computation and means to boost the production. This level of understanding creates the path to innovate new techniques to resolve industry level problems in quality control. As the non-destructive testing methods provided with no loss of the testing specimen and understanding the quality of the material after they are assembled. Such initial developments made the usage of NDT in quality control and effective results to determine the quality.

Latent heat thermal energy storage was widely used to solve the problem of the intermittency in time and space for solar energy systems. To improve the energy storage efficiency, metal fins were typically further added to the shell side to increase thermal conductivity of phase change materials (PCMs). However, the positive effect of metal fins on enhancing heat transfer has not been fully utilized. In this paper, a novel design on angled fins was proposed to improve the thermal transport for PCMs in a shell-and-tube thermal storage unit. A numerical model was built and verified by comparing with experimental observations on the melting front evolution and temperature history. Bending angles for fins ranging from 0° to 75° were designed upwardly and downwardly and quantified on the melting front shape and location, melting time, and temperature field. Results demonstrated that melting rates were improved for the angled-fin cases other than cases with large bending angles. The case with a 10° downward angle exhibited as much as 55.41% reduction in full melting time. Simultaneously, the temperature uniformity can be improved by 20.00%. The novel design strategy on fin angles engendered a promising solution to enhancing thermal storage for emerging engineering applications.

Friction stir welding (FSW), a solid-state joining process, is commonly used to join Aluminum alloys in aerospace, marine, car industry, and numerous industrial applications. Lightweight materials are commonly used in the transport industry to minimize component weight, and thin-walled structures are increasingly being used as energy-absorbing components in the industry. Even though FSW of plates is well established, FSW of pipe is still at the laboratory level. In this work, FSW for 6063 aluminum alloy pipe has been experimented through a novel procedure and it’s flexural and crashworthiness studies are carried out. The attempt of FSW is performed with a unique welding fixture mounted on a traditional milling machine. The crashworthiness test is conducted to analyze the ability of the structure to nullify the life loss during impact and the crash force efficiency of the pipe is identified. It is further analyzed for the flexural test to identify the bending load of welded aluminum alloy pipes. This study also exposes the basic understanding of the FSW procedure and its metallurgical implications of a friction stir welded pipe.

Welding is one of the join processes of any materials with usage of filler metal along with addition of heat, pressure on the surface parts. Gas Tungsten Arc welding (GTAW) is one type of joint method in which electric-arc formed and preserved amid non-consumable electrodes. the aim of this particular paper is to comparing the defects instigated of welded-Joint and mechanical behaviors such as tensile testing, bending, hardness, and impact test under various loads and conditions performing on work specimen in destructive testing. The effort of butt joints is made on stainless steels 304(SS304) plates via TIG welding apparatus the inner defects of specimens found from radiography testing in Nondestructive testing. Finally, explore the performance and conditions of TIG welded- plates after completing the work to compare radiography testing defects and mechanical properties.

In recent years, utilizing energy dissipation devices in building structures has been of great concerns due to the severe earthquake activities around the world. The performance evaluation of friction devices, buckling restrained braces and structural fuses as the recently introduced control systems proved their usability in dealing with different structural systems; however, there has been an increasing interest in decreasing the overall cost of the controlled building structures by developing devices with lower levels of complexity, reusable and easy to be implemented and manufactured after severe vibrations. The main objective of this paper to propose Boxy Bending Damper (BBD) as a novel energy dissipation device with partially lower constructional cost which prepares acceptable levels of stiffness, damping and ductility. This device is constructed by utilizing standard stainless-steel plates and bolts without any welded joints which provides a device with lower constructional complexity and can be considered as an improvement in the passive control devices. The performance of this new device is evaluated through the numerical and experimental analysis in which the optimal geometric configuration of the energy dissipation device is achieved by conducting multiple numerical analysis. The experimental tests have been conducted in order to evaluate the overall feasibility of the device in practice in which a cyclic test is carried out by means of a universal testing machine with maximum displacement of 75 mm. Besides, a parameter identification process is also conducted in order to calculate the required dynamical parameters of the device such as the stiffness, damping and ductility. The overall performance of the device in the experimental and numerical testing processes proved that the proposed device is capable of increasing the energy dissipation levels of structural systems by providing 35% of equivalent viscous damping and ductility ratio of about 33.

The accuracy of different fire design methodologies for hollow cross-sections subject to compression and major-axis bending is studied and compared in this paper. For that purpose, a numerical model based on shell finite elements is developed and validated against existing experimental results available in the literature. Comprehensive numerical parametric studies are then carried out by means of the validated numerical model, including different cross-section dimensions, loading conditions, steel grades and temperatures, to obtain a large set of results of the ultimate resistance of hollow sections in fire. Based on these results, the existing design rules of the Eurocode 3 Part 1–2, the AISC 360 specification and the recent design proposals of Couto et al. [1,2] and the Direct Strength Method adapted to fire are assessed in terms of their accuracy for predicting the section capacity, including the resistance against local buckling at elevated temperatures. It is demonstrated that the cross-sectional classification procedure for the case of fire, available in the Eurocode 3 and AISC specifications, results in inconsistencies and should be further investigated and revised in the future. To overcome the Eurocode 3 limitations it is proposed that the design methodology of Couto et al. [1,2] is adopted irrespective of the cross-section classification and for the AISC specification it is suggested the use of a reduced stress based on the 0.2% proof strength until more efficient design methods are developed.

This paper introduces a novel type of cold-formed steel box girder assembled from C-section flanges and sinusoidal corrugated webs, and the structural performance of such box girders was experimentally and numerically investigated. A total of seven cold-formed steel box girder specimens were fabricated by self-drilling screws and were tested subject to three-point bending. Prior to testing, the initial geometric imperfections of the sinusoidal corrugated webs were accurately determined using the 3D optical scanning technique. The structural behaviour of the tested box girder specimens, including load versus displacement curves and corresponding failure modes, was obtained and reported herein. The load-carrying properties of the adopted self-drilling screw connections were examined by separate single lap shear tests. Elaborate finite element (FE) models of the cold-formed steel box girders were developed by ABAQUS and were further validated against the obtained test results. Upon validation of the numerical models, the influences of key parameters including the number of screws, the corrugation ratio a/q, and the initial geometric imperfections were discussed in detail. It has therefore been recommended that the double-screw connections and appropriate corrugation ratios be adopted for design of cold-formed steel box girders with C-section flanges and sinusoidal corrugated webs.

Fused deposition modeling (FDM) is a practical 3D printing technology to print thermoplastic and composite materials. The FDM 3D printing process has gained substantial attention due to its capability to produce complex and accurate components. Recently, the wood particles-based filament in 3D printing has become a subject of interest, which is due to their prominent advantages, such as thermal resistivity, corrosion resistivity, biodegradable characteristics, and being environmentally friendly. Therefore, this research study aims to investigate the mechanical properties and statistical prediction model development for coconut wood–polylactic acid (PLA). The experimental investigation was carried out according to the ASTM standards (tensile—ASTM D638 Type 1, compression—ASTM D695, and bending—ASTM D790) at different infill densities (25, 50, and 70%) and five different infill patterns. The obtained results proved that concentric infill pattern accompanied by 75% infill percentage achieved the most outstanding tensile and bending behavior. For compression testing, grid infill pattern accompanied by 75% infill percentage exhibits maximum compression properties. In overall, the octagram spiral infill pattern shows the weakest properties among all the infill patterns. The experimental results were further analyzed using response surface methodology to identify the effectiveness of studied parameters on mechanical properties and to derive a mathematical model. The derived mathematical models related to studied mechanical properties have been proposed to predict the desired mechanical properties with respect to the variation of infill patterns and percentages.

Ribs in aircraft wings maintain the airfoil shape of the wing under aerodynamic loads and also support the resulting bending and shear loads that act on the wing. Aircrafts are designed for least weight and hence the wings are made of hollow torsion box and the ribs are designed with cut-outs to reduce the weight of the aircraft structure. These cut-outs on the ribs will lead to higher stresses and stress concentration that can lead to failure of the aircraft structures. The stresses depend on the shape of the cut-outs in the ribs and thus in the present work, the commercial software ANSYS was used to evaluate the stresses on the ribs with different shapes of cut-outs. Four different shapes of cut-out were considered to study the effect of cut-out shape on the stresses in the ribs. It was found that the best shape for the cut-outs on the ribs of wings to reduce weight is elliptical.

Flexible pipes are complex structures made of different layers and different materials. They are used in the oil and gas production in the off-shore platforms to conduct the oil or gas between different units, such as platforms, Christma's tree and transportation ships. The internal carcass of flexible pipes is made of duplex stainless steels type 2205 (UNS S32205 or S31803). In the production line, sheets of 1.8 mm thickness of this material are submitted to uncoiling and cold bending operations to form “S” profiles which are assembled to form the internal carcass. The end of one coil is welded to the begin of another, to make the process continuous. The welding process is autogenous automatic gas tungsten arc (GTAW). This work analyses the microstructure and corrosion resistance of the weld metal and compares to the base metal. Besides, non-destructive tests and electrical resistance measurements were conducted in the welded joint and base metal. The samples analyzed were from a flexible pipe manufacturer. It was concluded that the joints of this producer were not heat treated, which results in inadequate microstructure and lower corrosion resistance in the weld metal.

Thin-walled pipes have been widely used in chemical facilities and propulsion structures, where the distortion problem induced by welding fabrication is common and prominent, deteriorating assembly accuracy and even reducing load-bearing capacity. External constraint has shown great capacity to control the residual stresses and welding deformation. The objective of this research is to investigate the effect of constraint on welding process in thin-walled 304 stainless steel pipes through experiments and numerical simulation. To include the clamping effect in the welding simulation, the external constraint was modeled as the additional heat dissipation and mechanical restraint. The seam welded pipes with and without constraints were both modeled for comparison purpose. Good agreement was obtained between numerical modelling and measurements in both pipes. The results show that the welding deformation and residual stresses are both obviously reduced under the effect of external constraint, which was found to work mainly in the cooling process by generating more tensile plastic strain so as to reduce the shrinkage force in both axial and hoop directions. The maximum distortion is observed on the middle section of constrained pipe and on the end sections in the unconstrained one, which is caused by the combined effect of bending direction on the circumference and shrinkage force in the axial direction according to the inherent strain analysis. Moreover, the analysis of welding deformation mode reveals that the inward bending induced by hoop constraint contributes to the dimensional accuracy of the pipe ends under axial shrinkage forces. Parametric simulation analysis of the external constraint strategy was performed, and the results showed that reducing the constraint distance was the most effective way to mitigate welding distortion in seam welded pipes.

The beauty of the beach and underwater of Bangsring beach make this beach one of the leading destinations in Banyuwangi Regency. However, until today how to enjoy the beauty of the underwater can exclusively be done by diving or snorkeling, which is quite troublesome and exhausting, especially for tourists who want to enjoy and looking entertainment in a simpler way. So the concept of bottom-glass in this design is offered as a problem solving in this study, while the concept of flat plate and flat-bottom is carried out to efficiently time and cost of shipbuilding, because with this flat plate concept, there is no rolling and other material bending process. The design of the main dimensions is made based on owner requirements are obtained based on field study and literature studies, then the main parameters are obtained (LOA = 12 m, total B = 5.6 m, B each hull = 0.94 m, hull spacing = 3.72 m, T = 0.7 m, H = 1.85 m, Vs = 10 knots). To maximize the design, 4 ship models were designed with these primary parameters, based on the analysis of resistance using Maxsurf Resistance, model 4 with a maximum resistance of 4.3 kN was chosen which tend to be more effective compared with the designs of model 1, model 2, and model 3 which has a maximum resistance of 8 kN, 4.9 kN and 5.3 kN. The results of the stability analysis carried out in this design with the load case 100%, 80%, 60%, 40%, and 20%, has met all requirements for intact stability IMO MSC.36 (63) for HSC multihull Annex 7.

Three dimensional (3D) tubes, which possess the characteristics of space saving, lightweight and high strength, are widely used in many high-end industries such as aviation, aerospace, automobile and shipbuilding. However, when manufacturing a 3D tube in flexible bending process, springback is a big obstacle for improving the forming quality. In this paper, a new comprehensive strategy for springback control of 3D tubes is proposed. The strategy can be described as follows: (1) define the desired shape and manufacture shape; (2) optimize the manufacture shape using two tooling design methods (e.g. DA (displacement adjustment) method and BT (3) make a discretization of the manufacture shape to acquire the optimized forming parameters. Additionally, experiment is implemented to validate the effectiveness of the new strategy. Results show that forming parameters acquired by the new strategy are partially effective. The new strategy also demonstrates that, during 3D tubes forming, the deviation caused by over-bent elements can be counteracted by the deficient-bent elements. This principle is helpful to reduce the difficulty of parameter determination in future.

A novel method to improve the robustness of steel end plate connections is presented in this paper. Existing commonly adopted techniques alter the stiffness of the beam or the end plate to improve the connection’s robustness. In this study, the robustness is enhanced by improving the contribution of the bolts to the rotational capacity of connections, the higher the bolts’ elongation, the higher the rotational capacity that can be achieved. However, the brittleness of the bolt material, combined with its small length, results in negligible elongation. Alternatively, the load path between the end plate and the bolts can be interrupted with a ductile element to achieve the required elongation. This can be achieved by inserting a steel sleeve with a designated length, thickness, and wall curvature between the end plate and the washer. The proposed sleeve should be designed so that its ultimate capacity is less than the force in the bolt at failure, accordingly, the sleeve develops a severe bending deformation before the failure of any connection components. Using a validated finite element model, end plate connections with various parameters are numerically investigated to understand the performance of the sleeve device. The proposed system substantially enhances the rotational capacity of the connections, ranging between 1.37 and 2.46 times that of the standard connection. It is also concluded that the sleeved connections exhibit a consistent elastic response with the standard connections, indicating the proposed system is compatible with codified elastic design approaches without modification. Furthermore, for a specific connection, various ductile responses can be achieved without altering the connection capacity nor configuration.

A Building 3-storey construction project using reinforced concrete construction was failure and collapse in Johor Baru Central Jakarta. The impact of construction failure is work accidents (injury and death), damage to construction/infrastructure, and there are legal consequences for failures that occur and the causes of failure. The research method is to examine the condition of the installed structure, check the level of damage, test the quality of concrete, structural modeling with SAP (Structure Analysis Program) 2000, analyze and calculate the strength of the column cross section, analyze and conclude from the overall inspection results with implementing regulations and reinforcement in SNI 03 -2847-2002. The results of the study concluded that the initial failure was in the column with a size of 33 x 10 centimeters on the south side of the 1st floor with a buckling type failure that caused it to collapse due to pressure from above (floors 2 and 3). The results of the structural modeling of the SAP 2000 program and the calculation of the column cross-sectional strength obtained that the cross-sectional strength capacity of the column is 32.80 tons, this value is still able/safe to withstand the load of the structure above it. The failure and collapse of the column was caused by the implementation of the principles and details of the reinforcement that were not standardized and did not follow the rules of SNI 2847:2013 on the spacing of the stirrups and the details of bending of the iron.

Roll forming is increasingly used in the automotive industry for the manufacture of structural and crash components from ultra-high-strength steel (UHSS). Springback and end flare are common shape defects in roll forming and increase with material strength. The conventional roll forming process is limited to the manufacture of components with a uniform cross section while flexible roll forming can produce parts with variation in width and depth. In this paper, the flexible roll forming of an automotive component from three different high-strength sheets of steel is investigated. The experiments are carried out with a flexible roll forming prototyping facility and combined with finite element analysis. The study shows that the flexible roll forming of high-strength automotive components is possible. Springback and end flare depend on the material strength and the forming sequence and can be reduced with a flexible forming approach where the material is first overbent followed by bending back. Wrinkling of the flange was observed but the severity of wrinkling reduced with an increasing number of forming passes.

This paper describes a simplified methodology for the assessment of unreinforced masonry (URM) walls under out-of-plane two-way bending seismic action. The methodology involves a force-based check derived from the principle of virtual work. This check is proposed based on experimental observations of significant cracking resistance associated with two-way spanning URM walls, indicating methodologies considering such walls to be pre-cracked or to be non-laterally supported as overly conservative. The methodology incorporates several findings and developments from recent experimental campaigns: ranging from novel characterization tests on masonry couplets to incremental dynamic tests on full-scale buildings. Such incorporations include new formulation to calculate the torsional shear strength of a bed joint and accounting for possible changes in the boundary conditions of an OOP wall during dynamic loading. Testing standards as well as recommendations in several international guidelines for masonry structures addressing the input properties required to implement the proposed methodology are enlisted and reviewed. The methodology requires the definition of the period of vibration of the assessed URM walls, to calculate which plate theory based formulation is provided. Open research questions and potential avenues for further development of the methodology are ultimately highlighted.

This research presents the mechanical performance of self-tapping screw-reinforced slotted-in bamboo-steel-bamboo (BSB) connections and the corresponding capacity models. The yield strength of self-tapping screws (STS) and bolts commonly used in practical constructions were obtained through the three-point bending tests. The withdrawal tests of the screws from the engineered bamboo panels were reported. The BSB connections using STS reinforcement in different positions were studied, and the performance and mechanical parameters were compared with the connections without reinforcement. The test results show that STS application in the BSB connections can significantly improve its ductility and bearing capacity. Compared with the connection without STS reinforcement, the bearing capacity and ductility of the reinforced connection with STS reinforcement near the top were increased by 8% and 3.8 times. For STS application near the bottom and at both ends, the increased values were 26% and 4.3 times, 35% and 4.6 times, respectively. The brittle row shear failure mode of the unreinforced BSB connections can be changed to be the ductile yielding failure modes by applying STS reinforcement reported in this study. Based on the existing theoretical models, the capacity predictions of the BSB connections based on two different failure modes were calculated and compared with the test results. According to the experimental research conducted in this paper, it is strongly recommended that the STS reinforcement be used in the unidirectional bamboo connections to confirm the ductile failure modes, which can be estimated through the well-established European Yield Model (EYM) included the current design standards.

Improving the mechanical efficiency is not the most important objective in the design of wind turbine gearboxes since the available wind energy is abundant and costless. The most important criteria for dimensioning the gearbox are the fatigue strength—bending and pitting—, noise emission, vibrations, and maintenance requirements. Nevertheless, mechanical losses increase the lubricant temperature and induce thermal stresses, which increases wear and cracking risk. This means that friction losses should be reduced as much as possible, but always regarding the contact and tooth-root stress levels, as well as the other operating parameters which should be kept for ensuring the required operating conditions.In this paper, a study on the variation of the friction losses with the tooth shift coefficients is presented. All the other geometrical parameters—number of teeth, tooth height, pressure angle, helix angle, face width, and center distance—are unalterable, since all of them have been chosen according to more important design requirements. In addition, to keep the contact and tooth-root stress levels, the shift coefficients of the sun, planets and ring are calculated in such a way that the transverse contact ratios are kept, and therefore the critical load points for bending and pitting are also unchanged. The radial clearance is also kept in order to allow the proper evacuation of the lubricant. Finally, all the geometrical constraints (undercut, pointing, root interference, secondary interference, backlash) are also imposed. With all these restrictions, the optimal shift coefficients for all the gears are calculated to minimize the friction losses.

In this work, the influence of material models used in the FEM simulation on the springback prediction is investigated. The interest of this paper is to extend the knowledge base regarding springback predictions in numerical simulation. The springback effect of a V-shaped sheet metal part made of TRIP steel, with a thickness of 0.75 mm was investigated. The bending angle was set to 90°. In the numerical simulation, Hill48 and Barlat yield criteria were used in combination with Ludwik's and Swift's hardening models. Achieved data from the numerical simulations were compared and evaluated with experimental test results. The experimental results showed the relation between springback and calibration force. The effect of specimen cut direction on the springback was smaller in comparison with the calibration force. The numerical results of the springback were not identical with the experimentally achieved springback values in most cases. Particularly, when a calibration force of 1 800 N was used in the simulation. The simulation results showed a good correlation between experimental and numerical results, when Hill48 and Barlat yield criteria were used in combination with Ludwik hardening law and calibration force F with the value 900 N was applied.

The continuing efforts of automotive technology aim to deliver even greater safety benefits and reduce the weight of a vehicle. Thin-walled beams (TWB) are widely used as strengtheners or energy absorbers in vehicle bodies due to their lightweight and excellent energy absorption capacity. Thus, researchers are interested in the collapse behaviour and mechanical properties of thin-walled beams under static and dynamic loadings. Circular TWB is commonly used in vehicle side doors. In the event of a side collision, this beam deforms and absorbs the greatest amount of impact energy. In this study, the energy absorption capability and crashworthiness of polygonal cross-section TWBs subjected to lateral impact was investigated using numerical simulations. Polygonal TWB ranging from square to dodecagon, as well as circular cross section, were selected for this study. Energy absorption (EA), specific energy absorption (SEA) and crash force efficiency (CFE) crashworthiness indicators are employed to evaluate the bending collapse performance. Because TWB thickness and weight have a greater impact on bending performance, they were kept constant across all polygons. In ABAQUS explicit dynamic software, finite element simulations are performed, and plastic hinges and flattening patterns of all polygons are examined. The results show that heptagon, octagon, and nonagon cross-section TWB perform better in crashworthiness than square and circular TWB.

Heat-assisted rotary draw bending (HRDB) is a promising technique for manufacturing difficult-to-form tubular components comprising high-strength titanium tubes (HSTTs) with small bending radii. However, as a multidie constrained and thermomechanical coupled process with many uncertainty factors, a high risk of several defects, such as cross-section distortion, over wall thinning, or even cracking, is present. Achieving the robust design optimization (RDO) of complex forming processes remains a nontrivial and challenging scientific issue. Herein, considering a high-strength Ti-3Al-2.5V titanium alloy tube as a case material, the five significant uncertainty factors in HRDB, i.e., temperature distribution, tube geometrical characteristics, tube material parameters, tube/tool friction, and boost velocity had been analyzed. Subsequently, considering the preheating and HRDB of HSTT, a whole-process thermomechanical three-dimensional finite element model was established and validated for virtual experiments. Further, considering the maximum section distortion Q and maximum wall-thickness thinning t as the optimization objectives and the mean and variance of material and forming parameters, an RDO model was established. Finally, the Pareto optimal solutions were obtained using the nondominated sorting genetic algorithm II, and a minimum distance selection method was employed to obtain the satisfactory solution. Results show that the optimized solutions considering the uncertainty factors reduce the maximum section distortion rate of HSTT after bending by 38.1% and the maximum wall-thickness thinning rate by 27.8%.

Linear friction welding (LFW) is widely used for the fabrication of high-value components in the aero-industry. The versatility of use and high integrity of joints produced by LFW, suggest that this technology could contribute greatly to sustainable engineering of the future. For example, in near-net-shape manufacturing, LFW is predicted to offer a substantial reduction in material waste and processing time, in addition to offering the capability of bonding material pairs currently difficult to fusion weld. LFW of steel components is seldom researched in published literature, with little information available on fatigue strength and fracture behaviour of such joints. This may hamper the confidence needed to popularise LFW in wider industry. Thusly, authors conducted a discovery-oriented fatigue study, followed by metallography and micro-hardness tests, conducted on a 100Cr steel LFW coupon and corresponding batch of parent material. The weld coupon was dissected into a set of fatigue specimens, to allow mapping of the joint's internal properties through individual fatigue estimates and fracture morphology of each specimen in the set. A prototype fatigue machine was constructed, designed to deliver independent displacement and force controlled bending or torsional loadings, representing complex real-world conditions more accurately than common, uniaxial tests. The hour-glass shape of fatigue specimens allowed for targeting strictly the weld region, inducing fracture at the weakest material section, which was found to lay far outside the immediate contact interface. Referencing distances from fracture points to the theoretical weld interface plane in each fatigue trial, resulted in discovery of a macroscopic pattern. Interpolated to a crack initiation plane, this pattern is proposed to reflect the heat-affected zone, across the greater LFW coupon. Authors also studied crack paths and suggest a link between fracture direction, residual stresses in joint and angular orientation of the crack initiation plane in respect to the theoretical weld interface.

In steel structures, owing to technological aspects, frequently bolting access is difficult. To overcome these issues, technological research has proposed in the last decades several blind bolt systems that allow the installation of a bolt working only on one side of the connection. The simplest type of blind bolt is the thread-fixed one side bolt (TFOSBs), in which the connecting elements are fastened through threaded holes, and the connection is assured by the contact between bolt and hole threads. This type of bolting system is very easy to apply, but, currently, there are only a few design rules available. While the mechanical behaviour of TFOSBs is conceptually easy to understand, there are still some specificities that need to be accounted for and deserve specific investigations. A first aspect regards the behaviour in tension that must be characterized properly because it depends on some local effects such as the threads’ bending both bolt and hole. Similarly, regarding the behaviour in shear, due to the lack of confinement in the nut area, as already shown for similar bolt typologies, the bearing resistance may be lower compared to standard assemblies. To provide design rules for the behaviour of TFOSBs in tension and shear, in this paper, FE models and parametric studies are developed. The collected data are used to provide a prediction of the resistance of these fasteners, suggesting design rules of immediate applicability developed along the same lines of Eurocode 3 part 1.8 provisions. The results obtained suggest that, compared to standard bolt assemblies, an average reduction of 15% of the bearing resistance should be considered for the design of TFOSBs. Instead, for what regards the behaviour in tension, the shank necking failure of the bolt be achieved only by assuring minimum bolt screwing depths, which are suggested in this paper, confirming similar proposals already available in technical literature. Conversely, provided that the failure of the hole’s threads is accepted a reduction coefficient of the tensile resistance to be used in design, ranging from 0 to 1, has been proposed based on the FE studies’ results.

In the event of damage to additively manufactured components whose shape cannot be produced by machining, an additive repair can potentially be not only ecologically but also ecologically more favorable than the production of a new component. In addition, a number of hurdles that otherwise often impede the use of additive repair, e.g. the availability of the material of the damaged component for the additive process, are eliminated. As far as the authors are aware, this publication is the first to present a process for the additive refurbishment of additively manufactured components using the example of a wheel carrier. In this context, the possibility of increasing the fatigue strength of a structural component in refurbishment is discussed for the first time. To increase the fatigue strength of the wheel carrier, the chosen approach is to integrate the effect of particle damping into the component. Particularly in the case of components subjected to bending stresses, the effect of particle damping can be integrated into the component's interior without having to accept a significant loss of strength.

A V-bending experimental setup has been designed, to analyze the impact of blank geometry and process parameters over the springback in hot-rolled high-tensile-strength sheet metals (JSH590 steel). In this setup, a hydraulic press having the ability to vary load and holding time has been used. JSH590 sheet-metal blanks with varying geometric parameters are bend to acute, right and obtuse angles. Springback in each blank is determined which is found to be varying due to the different combinations of blank geometry and process parameters. To analyze the significance of thickness, width, bend angle, applied load and holding time, analysis of variance is applied, regression model is also derived relating the parameters with the springback, and finally, Genetic Algorithm has been applied to optimize the process parameters for the minimum springback. The outcomes of the research can be used in the industry, to evaluate the outcome in very-high-tensile-strength steel sheets.

Sheet springback and structural deformation of the folding mechanism are key issues in the sheet metal–forming process. Elastic-plastic bending theory and numerical simulation are applied to study the forming performance of sheet metal. First, a springback prediction model under general assumptions is established, based on the constitutive relationship of the elastic-plastic linear hardening material. In addition, the influences of processing parameters, such as sheet thickness and forming angle on springback, are analysed according to the theoretical model and verified by experiments. Then, a laser tracker is used to acquire the folding trajectory, and the structural deformation of the folding mechanism is confirmed by trajectory comparison. On this basis, numerical simulations are performed to collect deformation parameters, and a formula for mechanical compensation is obtained by linear fitting to the simulation data. Finally, experimental tests are carried out to verify the accuracy of the compensation model. The results show that the forming precision of the sheet metal can be controlled in the range of $\pm 10^{\prime }$ . The proposed method is generally applicable to linear hardening materials and operation conditions where the sheet thickness ranges from 0.8 to 3 mm.

Objective: To design, fabricate and evaluate the new features of a portable manual rebar bender, a Hand Tool that is used for bending rebar and other malleable materials. Methods: The researcher improves on the previously available portable manual rebar bender. Experts assessed the acceptability of this bender in terms of design and portability. Furthermore, as previously stated, the study significantly improves the usefulness of the inexpensively produced bending machine for reinforcing concrete with negligible human force. Findings: The device created has a valuable impact on the construction industry’s human force due to its affordability and marketability. Also,the present tools guaranteed strength, durability, and lightness in weight. Furthermore, the portable manual rebar is made of different elements such as a center axle, stationary backup roller, and sleeve. The results after ten trials showed that the portable manual rebar bender could finish 9 mm, 20mm, and 12 mm stirrup at an average of 24.3 seconds, 26.3 seconds, and 27.7 seconds, respectively. Additional results from seven to ten trials showed the bending time for 24 seconds stirrup for 9mm, 26 seconds stirrups for 10 mm, and 28 seconds stirrup for 12 mm. Furthermore, after a series of ten trials, the instrument achieved an accurate angle bent of 90 degrees. The M= 4.77 and 4.82 are very acceptable in terms of design and portability tools based on the evaluators’ rating. Novelty: The design is novel in terms of cost, portability, and efficiency. The device can be a great help in the structures and buildings. Furthermore, the construction industry will use the portable manual rebar bender to build houses and other local infrastructure to test its effectiveness. Then, the researcher is encouraged to engage in another research to try the innovation. Keywords: Improvised; Innovative; Locally made; Device; Bender

The problem of springback is one of the most significant factors affecting the forming accuracy for aluminum 3D stretch-bending parts. In order to achieve high-efficiency and high-quality forming of such kind of structural components, the springback behaviors of the AA6082 aluminum profiles are investigated based on the flexible multi-points 3D stretch-bending process (3D FSB). Firstly, a finite element simulation model for the 3D FSB process was developed to analyze the forming procedure and the springback procedure. The forming experiments were carried out for the rectangle-section profile to verify the effectiveness of the simulation model. Secondly, the influence of tension on springback was studied, which include the pre-stretching and the post-stretching. Furthermore, the influences of the bending radius and bending sequence are revealed. The results show that: (1) The numerical model can be used to evaluate the effects of bending radius and process parameters on springback in the 3D FSB process effectively. (2) The pre-stretching has little effect on the horizontal springback reduction, but it plays a prominent role in reducing the springback in the vertical direction. (3) The increase of bending deformation in any direction will lead to an increase of springback in its direction and reduce the springback in the other direction. Besides, it reduces the relative error in both directions simultaneously. This research established a foundation to achieve the precise forming of the 3D stretch-bending parts with closed symmetrical cross-section.

This paper demonstrates the concept of adaptive repurposing of a portion of a decommissioned Clipper C96 wind turbine blade as a pole in a power transmission line application. The current research program is aimed at creating a path towards sustainable repurposing of wind turbine blades after they are removed from service. The present work includes modelling and analysis of expected load cases as prescribed in ASCE 74 and NESC using simplified boundary conditions for tangent pole applications. Load cases involving extreme wind, concurrent ice and wind, extreme ice, differential ice, broken conductor, and broken shield have been analyzed and governing load cases for bending, shear, and torsion have been examined. Relative stiffnesses of different parts forming the wind blade’s cross section (i.e., shell, web, and spar cap) are determined. The corresponding stresses associated with each part under the governing loads are compared to allowable strength values which are determined from composite laminate theory and modelling of the known laminate structure of the E-Glass FRP material. Stresses and deflections obtained are compared with governing reliability-based design criteria and code requirements. The results of the structural analysis indicate that the wind blade can resist the expected loads with reasonable safety factors and that the expected deflections are within permissible limits. Recommendations are provided for detailing and modification of the wind blade for a power pole application in which crossarm and davit connections are highlighted, and foundation details are emphasized.

The article discusses the mechanical properties and cold resistance of austenitic stainless steel (analogue 07Cr25Ni13) obtained by 3D printing by electric arc surfacing from ER309LSI welding wire on a CNC machine. These properties were investigated in the process of physical tests of samples cut along and across the layers of 3D printing for tensile and impact bending. Using optical microscopy, the microstructures of steel sections were obtained for various temperature conditions of interlayer exposure, as well as the values ​​of the recommended microhardness. In the process of 3D printing, an intelligent system for monitoring the dynamic stability of the electric arc was applied, which made it possible to guarantee the stability of the structure and properties of the obtained samples throughout the entire process of surfacing. Additional heat treatment of experimental samples (austenitization) was considered as a way to improve mechanical properties and cold resistance. It has been established that the dynamic stability of an electric arc, modes of interlayer temperature holding and subsequent heat treatment largely determine the mechanical properties and cold resistance of ER309LSI steel obtained by 3D printing by electric arc surfacing.

Morphing leading edge has great potential for noise abatement and aerodynamic efficiency improvement. The drooping effect is realized by bending of the flexible skin which encloses to form the leading edge. Since the flexible skin is often made of composite laminates of Glass Fiber Reinforced Plastics (GFRP), the lay-up sequences have become the determinant, which affects not only the morphing quality but also the manufacturing complexity. Two optimizing methods of lay-up sequences are comparatively studied. In the first method, the laminal quantities in 0°, ±45° and 90° vary independently, while in the second one, the concept of isotropic laminate unit [0/45/−45/90]s is employed and the unit quantity is the unique variable. Final evaluation demonstrates that for both methods there is insignificant impact to the overall morphing quality; however, specific concern is equally necessary for these two methods to the tip of the leading edge where the skin is at its minimum thickness and bears the most severe bending deformation. In terms of computational efficiency and post-processing labor, the second method has better performance.

The existing cross arms in high transmission towers are made of pultruded glass fibre reinforced polymer composite (PGFRPC). The moisture, temperature change in the atmosphere, and other environmental factors affect the performance of these members and cause a complete failure. It is apparent that any material used in such applications is susceptible to attack from environmental factors. Therefore, a feasible solution for this issue is to enhance the PGFRPC with a composite-filled sandwich structure as an alternative that could sustain longer than the existing cross arms due to its superior performance under bending and compressive loads. This paper presents a case study on experimental and analytical mechanical performance of both PGFRPCs and composite-filled sandwich structure. In this review, the composite-filled sandwich structure is proposed as an alternative to the conventional PGFRPC.

Motion analysis techniques are well-known for quantitative and objective human skills evaluation in various applications, including sport and medical skills training and development procedures. Such analysis invariably requires reliable data acquisition and analytical tools that can effectively monitor the human body movements. This paper introduces a novel soft and stretchable strain sensor for joint angle measurement applications. The strain sensor is made of ultrathin gold nanowires, which is highly stretchable, and sensitive. However, the electrical response of the sensor involves nonlinearity and hysteresis. To tackle this problem, we propose to use a machine learning algorithm to characterise the sensor for enhancing the predictability of the sensing response. A sensor embedded hinge system is developed for automated measurement of bending angle to validate the characteristics of the developed sensing system. The sensor has a high gauge factor of about 12 and shows high durability during a repeated stress-and-release test. It could measure the bending motion with an error of less than 2°. The developed sensor, combined with the proposed machine learning algorithm, can accurately monitor the bending motion. We believe that our sensing technology has great potential to be used for the evaluation and improvement of human skills proficiency.

The types and methods of modifications of teeth and gear wheels, which have found application in gearboxes of aircraft and helicopters, are presented. Features of geometry, parameters of different types of initial produced contours, their modifications, application and influence of various factors on improving the operational characteristics of gear drives of aviation gearboxes are considered. Arcuate (short and long) and short linear options for modifying the tooth profiles of aircraft gearboxes are best suited to absorb the errors of spur gears. There was no significant difference in the use of short and long correction for a relative decrease in temperature in the contact zone of the wheel teeth, therefore, the use of any correction of the tooth profile, with rare exceptions, turns out to be useful. The advantages of using increased profile angles in comparison with the standard ones used in general mechanical engineering are considered. Development of designs of teeth and gear wheels in aircraft gearboxes, the use of gears with teeth of an asymmetric profile, which can be considered as a cardinal modification of the tooth profiles. The use of such gears increases the strength of the teeth due to the increase in the thickness of the teeth. Unsymmetrical teeth have a large thickness at the tip, which reduces teeth chipping and due to their greater height, greater smoothness of engagement is achieved, bending and contact stresses are reduced. The most radical type of modification is the use of asymmetric profiles of the teeth of the wheels of aircraft gearboxes.

This paper presents a parametric study of the optimization design for T-shaped deep cement mixing (TDM) and conventional deep cement mixing (DCM) columns improved soft soil for supporting embankments. The objective of the optimization was to find the best compromised solution for the cost effectiveness in conjunction with minimizing the serviceability limit state (SLS) requirements (i.e., settlements, differential settlements, and lateral movements) while maximizing the ultimate limit state (ULS) requirement (i.e., factor of safety against bending failure). A combination between a genetic algorithm and the response surface method was employed as an optimization approach for determining the optimal solution. The relations and interpretations between design column parameters and design requirements are presented and discussed through parametric studies. The optimization results indicate that the optimal TDM column can allow to permit a lower construction cost than the optimal DCM one.

Wearable and portable electronic devices based on textile structure have been widely used owing to their wearability and comfortableness. However, yarn fineness and the comfort of the fabric cannot satisfy the requirements of smart wearable devices. This work presents a novel strategy to prepare highly integrated PVDF/conductive nylon core-sheath structure piezoelectric yarns for wearable which is fabricated by combining electrospinning strategy with 2D braiding technology. The fineness of single yarns as well as strength are both improved significantly compared to previous works. The piezoelectric outputs of the yarn are still stable after 800 s fatigue test at a frequency of 4 Hz, and the cycle stability can maintain more than 3200 cycles. Furthermore, the piezoelectric yarns are further woven into piezoelectric plain fabric. According to the electrical performance, the length of the piezoelectric yarn and the thickness of the piezoelectric layer would both affect the output electrical performance. The yarn of the 10 cm in length and 600 μm in fineness can produce an output voltage of 120 mV. Meanwhile, Both the piezoelectric yarn and the fabric could generate piezoelectric output signals through human movement, such as bending, walking. Therefore, the electrical and mechanical performance of the piezoelectric yarns prepared in our work could be improved significantly, and the comfortableness and durability performance of the piezoelectric fabric can satisfy most wearing requirements, which would provide some help in the field of piezoelectric wearable devices based on yarns and fabrics.

Seismic demands on columns that belong to 10-, 14- and 18-story buildings structured with ductile concentrically braced frames (CBF) in a chevron configuration are studied in this paper. Buildings were carefully designed following principles of the capacity design philosophy, and they were virtually located in a soft soil condition. The research explores a more realistic assessment of the axial and bending demands on the columns of braced bays for a safe and economical design. Based on the statistical results of detailed nonlinear analyses, a procedure for estimating the axial design load in the columns of braced frames is proposed for mid- and high-rise buildings to obtain a conservative prediction of the demand. The methodology depends on the story where the column is located and the expected capacity of the bracing system calculated from a participation factor. Furthermore, a relationship between the building height and the accuracy of the prediction is underlined. The study also provides some detailed background behind the design procedure of CBF from specialized codes and compares the efficiency of published methodologies to estimate the design demands.

Purpose In manufacturing, dedicated machine tools and flexible machine tools are failing to satisfy the ever-changing manufacturing demands of short life cycles and dynamic nature of products. These machines are limited when new product designs are introduced. The solution lies in developing responsive machines that can be adjusted or be changed functionally when these change requirements arise. These machines are reconfigurable machines which are becoming the new focus, as they rapidly respond to product variety and volume changes. A sheet metal working machine known as a reconfigurable guillotine shear and bending press machine (RGS&BPM) has been developed. The purpose of this paper is to present a methodology, function-oriented design approach (FODA), which was developed for the design of the RGS&BPM. Design/methodology/approach The design of the machine is based on the six principles of reconfigurable manufacturing systems (RMSs), namely, modularity, scalability integrability, convertibility, diagnosability and customisability. The methodology seeks to optimise the design process of the RGS&BPM through a design of modules that make up the machine, enable its conversion and reconfiguration. The FODA is focussed on function identification to select the operational function required. Two main functions are recognised for the machine, these being cutting and bending; hence, the design revolves around these two and reconfigurability. Findings The developed design methodology was tested in the design of a prototype for the reconfigurable guillotine shear and bending press machine. The prototype is currently being manufactured and will be subjected to functional tests once completed. This paper is being presented not only to present the methodology by to show and highlight its practical applicability, as the prototype manufacturers have been enthusiastic about this new approach. Research limitations/implications The research was limited to the design methodology for the RGS&BPM, the machine which has been designed to completion using this methodology, with prototype being manufactured. Practical implications This study presents critical steps and considerations in the development of reconfigurable machines. The main thrust being to explore the best possibility of developing the machines with dual functionality that will assist in availing the technology to manufacturer. As the machine has been development, the success of the design can be directly attributed to the FODA methodology, among other contributing factors. It also highlights the significance of the principles of RMS in reconfigurable machine design. Social implications The RGS&BM machine is an answer for the small-to-medium enterprises (SMEs), as the machine replaces two machines with one, and the methodology ensures its affordable design. It contributes immensely to the machine availability by eliminating trial and error approaches. Originality/value This study presents a new approach to the design of reconfigurable dual machines using principles of RMS. As the targeted market is the SME, it is not limited to that as any entrepreneur may use the machine to their advantage. The design methodology presented contributes to the body of knowledge in dual reconfigurable machine tool design.

The major part of ongoing research in the field of robotics is to mimic the behaviour of species present in nature. This paper presents the workspace of the multi-section bionic manipulator Robotino-XT under the failure of one of its bellow. These types of failure may be due to repeated use, pressure leakage, hysteresis or improper design. The CBHA part of Robotino-XT has two bending sections, where each section has three bellows (actuator). Various strategies are proposed to compensate for the loss in workspace due to failure of one bellow. Also, the workspace obtained after the failure of the bellow is compared with the full-fledged workspace.

Additive manufacturing of electrically responsive soft actuators is of great importance in designing and constructing novel soft robots and soft machines. However, there are very limited options for 3D-printable and electrically responsive soft materials. Herein, we report a strategy of 3D printing polyvinyl chloride (PVC) gel actuators that are electrically controllable. We print a jellyfish-like actuator from PVC ink, which can achieve 130° bending in less than 5 s. With the multi-material 3D printing technique, we have further printed a soft actuator with a stiffness gradient that can generate undulatory motion. As a proof-of-concept demonstration, we show that a 3D-printed PVC gel-based smart window can change its transparency upon the application of voltage. The 3D printing strategy developed in this article may expand the potential applications of electrically responsive soft materials in diverse engineering fields.

In order to solve the problems of excess ovality and cross-section distortion of longitudinally submerged arc welding pipes after forming, a new three-roller continuous setting round process was proposed. This process can be divided into three stages: loading stage, roll bending stage and unloading stage. Based on the discretization idea, the mechanical model of the primary statically indeterminate problem of the longitudinally submerged arc welding pipes at the roll bending stage was established, and the deformation response was obtained. The simulation and theoretical results show that there are three positive bending regions and three reverse bending regions along the circumference of the pipe. The loading force of each roller shows growth, stability and downward trend with time. The error between the theoretical fitting curve and the simulated data point is very small, and the simulation results verify the reliability of the theoretical calculation. The experimental results show that the residual ovality decreases with the increase of the reduction, and the reduction of the turning point is the optimum reduction. In addition, the residual ovality of the pipe is less than 0.7% without cross-section distortion, which verifies the feasibility of this process.

Modelling the failure of engineering polymers used in critical structural applications is still a challenging task that is increasingly demanded by the industry to optimize part design and estimate component service life. The difficulties include not only developing constitutive models capable of reproducing the complex polymer response at a reasonable computational cost, but also calibrating related parameters. That is to say, a way to find specific parameters which best represent the actual behavior of a material within the scope and limitations of a given constitutive or failure model. The aim of this study is to contribute in developing a robust inverse method calibration strategy. To address this issue, a novel approach based on genetic algorithms optimization (GA) together with finite element analysis (FEA) is proposed to blindly extract key constitutive and failure parameters from instrumented impact tests on single edge notched bending (SENB) specimens. The method was implemented to infer eight constitutive and failure parameters of a polyamide 12 (PA12) with an elasto-plastic ductile damage model. Triaxiality induced stable-unstable transition was successfully achieved by varying the notch depth of SENB specimens. Accordingly, three optimization schemes were conducted: (i) using only unstable experimental data; (ii) using only stable experimental data and (iii) using both simultaneously (multi-objective). The set of parameters obtained from each scheme were used to perform predictive FEA simulations, which were verified with experimental data. It was proven that both propagation regimes provide substantial information to obtain the mechanical response of the material. Simulation results evidenced the capability of the proposed strategy to predict the PA12 impact response and furthermore to fairly reproduce a completely different load case: a dynamic tensile test.

The traditional method for detecting cracks in concrete bridges has the disadvantages of low accuracy and weak robustness. Combined with the crack digital image data obtained from bending test of reinforced concrete beams, a crack identification method for concrete structures based on improved U-net convolutional neural networks is proposed to improve the accuracy of crack identification in this article. Firstly, a bending test of concrete beams is conducted to collect crack images. Secondly, datasets of crack images are obtained using the data augmentation technology. Selected cracks are marked. Thirdly, based on the U-net neural networks, an improved inception module and an Atrous Spatial Pyramid Pooling module are added in the improved U-net model. Finally, the widths of cracks are identified using the concrete crack binary images obtained from the improved U-net model. The average precision of the test set of the proposed model is 11.7% higher than that of the U-net neural network segmentation model. The average relative error of the crack width of the proposed model is 13.2%, which is 18.6% less than that measured by using the ACTIS system. The results indicate that the proposed method is accurate, robust, and suitable for crack identification in concrete structures.

The aim of this paper is to construct a software containing a complete design procedure and detailed drawing for bevel gears (straight, skew, zerol and spiral). This software can be executed on all the IBM personal computers XT/AT or compatibles. The main elements of the design in this program are: input data, type of bevel gear, type and shape of gear tooth system (ISO, US, BS, DIN and Gleason), module, virtual number of teeth, minimum number of teeth to avoid Interference, tooth profile modification, shaft angle, contact ratio, face width, spiral angle, force analysis, sliding velocity and efficiency, material, equations for bending strength (Modified Lewis, Buckingham, AGMA and Gleason) and surface durability, also load carrying capacity for bending strength and surface durability using ISO, AGMA, Gleason and 8S equations with constant or variable tooth load. Many equations and practical formulae are selected for making the gear construction (integar gear, solid gear, gear with web, gear with web and holes, gear with arms and composite gear). With running the software, full specifications, geometry, kinematics. loads, stresses and detailed drawing of the gears are obtained according to the input data. Different examples are selected 10 show the variety of the output data and the strength of the software. Also these runs show the save in time and accuracy of the results.

In this research, computationally efficient testing protocols were developed for the accurate detection and quantification of nonlinearities in the bolted flange interfaces of aeroengine casing assemblies. Aeroengine casings are joined by bolted flanges that are exposed to high loading amplitudes, leading to bending and large deflections that cause structural nonlinearities. Initially, to assess these structural nonlinearities, a computationally efficient finite element (FE) modelling methodology was developed to accurately capture the vibrational characteristics of the casings while also significantly improving computational efficiency. The technical accuracy of the vibrational characteristics obtained from the FE modelling technique developed here was validated using simulation methods and experimental vibration testing such as modal analysis, the modal assurance criterion, and mode shape assessment. The modes most susceptible to nonlinear dynamic response were then theoretically identified using the mode shape results acquired through the FE model. Thus, a two-step experimental approach is proposed for achieving the accurate and time-efficient quantification of nonlinearities. In the first stage, a rapid experimental nonlinear assessment is performed using a stinger–shaker set-up to validate the FE simulation results of the susceptible nonlinear modes identified. In the second stage, a precise high-resolution measurement is taken with respect to the modes identified in order to precisely capture the nonlinear characteristics. The integration of the proposed theoretical FE modelling technique with advanced experiment formulations results in a significantly more time-efficient and accurate nonlinear testing protocol for aeroengine structures. Furthermore, the nonlinear damping and stiffness parameters of aeroengine casings were also explored in this research and analysed to improve the existing design and development strategies.