Welded Connections Research Articles

Application of DFMA in lock band service modification of ATB-I3 building machine

The locking mechanism on the band service, known as the lock band service, is used to move materials to the tire-making machine. A building machine is a device that assembles components into partially finished or green tires. The components are tread, which acts as the tire tread, band/ply, which are fabric sheets coated in rubber, and bead wire. Subsequently, the materials are put together on the drum-mounted construction machine. The ATB-I3 machine has the largest downtime owing to a band service fault, with 840 minutes in January 2024, and is the problem with the highest downtime in section A2. The cause of the excessive downtime in the band service is an issue with the band service lock system, namely the pneumatic movement lock mechanism on the band service component. As a result, adjustments must be made by altering the lock band service's design. After that, a weld joint strength analysis is performed to make sure the modification can be safely put into practice. To obtain the optimal modification design, the DFMA method is employed. With the use of the DFMA approach, the updated design—which had a design efficiency value of 4.23% to 4.31% before—was improved. The welding connection in the updated design is safe to use since, according to the results of the welding connection calculation, the lock band service holder has a maximum welding load of 294,645.08 N whereas the actual welding load is 147,928 N. The reduction in service band downtime was tested with this improvement. Following the implementation of the update in March 2024, the amount of downtime resulting from damage to the band service dropped by 445 minutes, or 52.97%, to 395 minutes

Cyclic axial loading tests on mortar-filled rectangular tube with various connection details

Although a mortar-filled rectangular hollow structural section (RHS) under monotonic loading has achieved large tensile capacity using various connection details and buckling capacity of RHS members, the structural capacity of the mortar-filled RHS tubes has not been investigated under cyclic loading. In this study, the seismic performances of newly developed mortar-filled RHS tubes with various connection details were evaluated under cyclic axial loading. The major test parameters included the end connection type, the thicknesses of the RHS tube, cap plate, and cleat plate, as well as the length of the RHS tube. The test results showed that the RHS tube in all specimens failed by tensile fracture before axial compression failure. The seismic performance of the embedded shear plate end connection with penetrating rebar was superior to that of a conventional welded T-end connection. The test results were compared with the current design code to evaluate the seismic capacity of the RHS tube according to the connection details. Design considerations for the connections of the mortar-filled rectangular tubes were also provided.

Investigation on effects of nano-reinforcement on the mechanical properties, fatigue, and microstructural analysis of dissimilar AA6061- Mg AZ31B weld joints

Weld joints have been subject to substantial improvement in mechanical durability and wear resistance in recent years. This research work challenge can be answered by incorporating nano-materials into the weld zone. Mechanical and metallurgical aspects of friction stir welded (FSW) butt joints made of AA6061 aluminum and Mg AZ31B alloys have been examined in this work, both with and without the use of naturally derived biochar nanoparticles. The biochar particle was extracted from rice husk. Throughout the whole weld joint manufacturing process, a tool with a rotational speed of 1400 rpm, a welding speed of 40 mm min−1, and a tapered pin profiled tool were employed. During the joint fabrication process, the constant axial load of 7 kN, plunge depth of 0.2 mm, and constant dwell time of 0.3 s were also maintained. In order to improve the mechanical attributes of the weld joints, different wt% of biochar such as 1%, 2%, and 3%, were applied at the interface region of the weld joints. The experimental results revealed that the percentage of reinforced nano-materials plays a significant effect in improving the weld joint qualities. The testing results of reinforced friction stir-welded joint qualities were compared to those of simple friction stir welded joints made without and with adding the nanoparticles. The best results were obtained when 2 wt% of biochar particles was added to the weld interface region. The presence of biochar nano-particles, in addition to their contribution to increased grain refinement in the weld nugget region, was also seen in the region. It was discovered that the event distribution of particles at the nugget zone significantly enhanced the mechanical and wear resistance qualities of the weld joints that were manufactured. The optical microscope was used to analyze the microstructures in the weld nugget region, and a scanning electron microscope (SEM) was utilized to examine the fracture analysis of the tensile samples. The presence of 2 wt% biochar particles in the weld nugget region resulted in a considerable increase in the mechanical characteristics of the weld connections. The ultimate tensile strength, hardness, and yield strength of the weld nugget results 197 MPa, 173 HV, 163 MPa. Overall, when compared to the qualities of the base material and plain weld joints. The mechanical properties and wear resistance of the weld joints have improved significantly. When biochar particles were used as reinforcement particles during the fabrication phase of the joint, a mechanism for pinning was observed in the weld microstructure.

Study on the influence of cap connection mode on the deformation of all-steel spiral anchor

Abstract Spiral anchors find widespread use across diverse projects, including residential, commercial, street lamp poles, photovoltaic systems, and transmission tower infrastructure, due to their simple structure, convenient construction, high degree of mechanization, and minimal soil disturbance. All-steel spiral anchors offer notable advantages in terms of ease and environmental friendliness. To bolster their utilization in power transmission engineering applications, based on the application requirements of the spiral anchor foundation of the Weifang Guanting transmission tower, the influence of the connection method of the bearing platform on the deformation of the all-steel spiral anchor is studied. The results show that both the welding and bolt connection methods can meet the required stiffness of the project.

Effect of Bias Arc on Microstructure and Corrosion Resistance of Q235/304 Dissimilar-Steel-Welded Joints.

To fully exploit the advantages of steel, the welding connection of dissimilar steels has been developed. In this work, the metallographic microstructures, elemental distributions, and electrochemical corrosion properties of the Q235 and 304 welds under different bias arcs were investigated. The arc bias caused the Q235-side heat-affected zone to widen, the microstructure consisted of ferrite and pearlite, and the ratio varied with decreasing distance from the fusion line. Elemental scans show that Cr and Ni concentration gradients exist near the fusion line. The 304-stainless-steel-side heat-affected zone was mainly composed of austenite grains, and the fusion zone was narrower but prone to cracking. Electrochemical tests revealed that 304 stainless steel had the best corrosion resistance, while Q235 had the worst corrosion resistance, and that the welded joints with an arc bias toward the 304 side had the best corrosion resistance. The samples' the passivation film which formed via electrochemical polarization had limited stability, but the over-passivation potential could be used as a reference for corrosion resistance. Overall, the arc bias and weld material properties significantly affected the microstructure and corrosion resistance of the joints.

Microstructure formation mechanism and mechanical properties of super-thickness TC11 titanium alloy joint by electron beam welding and laser additive manufacturing hybrid connection technology

Advanced connection technology for extra-large/super-thickness titanium wrought components is urgent demand in aerospace manufacturing industries. For achieving high-performance titanium alloy super-thickness joint with a high connecting efficiency, a novelty concept of hybrid connection technology with electron-beam welding and subsequent laser additive connection is proposed. A super-thickness (200 mm) TC11 titanium alloy joint has been successfully prepared, and microstructure, tensile properties and fracture behavior of different regions in which are investigated. The results suggest that in stress-relieve heat treatment (SRT) condition, deformation and fracture of the joint are prone to occur in its low-strength wrought base material zone; after double annealing heat treatment (DAT), lamellar α phases in different zones of the joint become similar, associating with a higher fraction of fine secondary α phases in wrought base material zone. Therefore, the tensile properties of the joint are comparable to wrought properties. Although strength in different zones of hybrid connection joint is similar, ductility is not uniform and apparently lower in middle fusion zone due to grain heterogeneity. Overall, these findings indicate that hybrid connection can be one potential technology for fabricating high performance super-thickness titanium alloy joint with a high connection efficiency in engineering application fields.

Enhanced comprehension of the cross-scale forming mechanism in CF/PEEK resistance welding: Analysis of temperature gradients and meso–microscopic phase transitions

Resistance welding technology is an effective solution for connecting thermoplastic composites. However, limited research on non-uniform distribution of interfacial temperature and complex evolution mechanism of phase-change molding hinders its application. This reliance on traditional experimental and trial-and-error methods severely impedes its development. Therefore, this study employed a novel cross-scale numerical simulation method, being applied for the first time in the field of resistance welding for elucidating the underlying mechanism of joint formation through multi-component phase transformation. The constructed model accurately represented the transient heat transfer of a realistic wire mesh structure in three dimensions, while incorporating complex gradient effects arising from both spatial and temporal variations in heating element temperature due to air interference. Further, melting, flow, and consolidation behavior of the resin matrix in resistance welding of carbon fiber/polyetheretherketone (CF/PEEK) thermoplastic composite was investigated herein at a mesoscopic scale. To accomplish this objective, a three-phase flow spatial forming and evolution model for resistance welding was developed at the mesoscopic scale by integrating principles from fluid dynamics. Interestingly, introduction of an air phase reinstated the spatial voids formation and flow in resistance welding, providing robust evidence for the initiation mechanism of internal defects. Moreover, this study revealed variations in the melting mode of PEEK resin across different regions within the weld and highlighted distinct distributions of voids resulting from uneven heat transfer. The interfacial phenomenon and flow diffusion mechanism between components in resistance welding tests were further verified and discussed through analyzing scanning electron microscopy and energy dispersive spectroscopy results. Temporal and spatial correlation in void distribution within the welding zone was observed, which was found to be consistent with simulation results. Specifically, with the progress of the welding process, air near the wire mesh gradually dispersed into the laminate, with significantly more voids at weld seam edges than in central regions. This research methodology based on stepwise scale reduction offers a promising avenue for investigating resistance welding and other connection forming applications, in particular, within the context of engineering underlying logical behavior.

Design and Performance Study of Carbon Fiber-Reinforced Polymer Connection Structures with Surface Treatment on Aluminum Alloy (6061)

The existing connection methods for aluminum alloy profiles primarily include adhesive bonding and mechanical connections, with metal welding being widely employed. However, metal welding connections exhibit issues such as low joint strength, significant welding deformation, susceptibility to surface oxidation, poor welding surface quality, and challenges in achieving thin-walled metal structures. This paper presents a novel aluminum alloy connection structure that utilizes carbon fiber-reinforced polymer (CFRP) composites to replace welding for connecting aluminum alloy profiles. This innovative aluminum alloy composite connection structure not only enhances connection strength but also addresses the difficulties associated with metal welding. Research indicates that the optimal width of the CFRP structure in the connector is 60 mm, and with synergistic treatment of the aluminum alloy surface, the connection enhancement effect is optimal. Under these conditions, the tensile load can reach 58.71 kN and the bending load can reach 14.33 kN, which are 375.38% and 380.87% higher than those of welded aluminum alloy connections, respectively. The mass-specific strength increases by 106.27% and 134.42%, respectively. Simulations of this connection structure in components demonstrate that it improves strength by 73.99% and mass-specific strength by 71.95% compared to pure metal welded connections. Using ABAQUS 2023 software for simulation and calculation, the difference between the simulation and experimental results is within 5%, verifying the feasibility of the designed structure. This study provides new insights and a theoretical foundation for the development and application of hybrid connection methods involving metal and fiber-reinforced composites.

Ultimate strength of welded aluminium stiffened panels under combined biaxial and lateral loads: A numerical investigation

The number and size of aluminium non-monohull ships have been steadily increasing over time. This raises growing concerns regarding their structural strength, especially considering the adverse effects of the heat-affected-zone (HAZ) on welding connections in aluminium structures. This paper investigates the ultimate strength of welded aluminium stiffened panels under combined biaxial compressive loads and lateral pressure through the application of numerical simulations. Altogether 360 cases are simulated with varied panel lengths, welding patterns and load combinations. The results are presented and discussed with respect to force end-shortening curves, failure modes and ultimate strength. Influences of the combined loads and HAZ effects are summarized. The numerical results are compared to two commonly used design methods in the marine industry, the International Association of Classification Societies (IACS) rule and the Panel Ultimate Limit States (PULS) approach. Their applicability to welded aluminium stiffened panels is discussed, and modifications are suggested with respect to the transverse loads, lateral pressure, and HAZ effects.

Mitigation of rockfall geohazards: Full-scale investigation of the performance of a practical baffle design for direct use in the field

To arrest rockfall boulders, baffles are constructed as steel members affixed on top of a concrete footing. Existing designs aim to prevent any footing rotation and steel member bending. As such, existing baffle designs require massive reinforced concrete footings and complex bolt and weld connections. Such designs have limited constructability and result in complex failure mechanisms (i.e., tensile failure of concrete foundation at connections). In this paper, we introduce a new baffle design concept that optimizes the balance between steel member bending and footing rotation to enable a compact design. Full-scale pendulum experiments are conducted to evaluate the proposed easy-to-construct and design baffle under successive boulder impacts of 50 kJ. It is demonstrated that by considering the effects of steel member deflection and concrete foundation rotation, the maximum impact force on baffles is reduced by up to two times when compared with those on a rigid barrier and the failure modes are simplified to either overturning failure of the footing or buckling failure of the steel member. A ratio that defines the flexural capacity of the steel member to the overturning capacity of the shallow concrete foundation is proposed to control the failure mode. The optimized baffle configuration for an impact energy of 50 kJ, with minimum residual deflection, has a target capacity ratio of 2.0.

Vibration Response of Metal Plate and Shell Structure under Multi-Source Excitation with Welding and Bolt Connection

There are many excitation sources and complex vibration environments in combine harvesters. The coupling and superposition of different vibration signals on the plate and shell seriously affect the working parts of the body. This also reduces the reliability of the whole machine. At present, domestic and foreign research on existing harvesters mainly focuses on harvesting performance, with less research on vibration characteristics. Therefore, in this paper, the vibration response of the metal plate–shell under the two connection modes of bolt connection and welding is studied, in order to optimize the design and structure of the plate–shell structure of the combine harvester and improve the overall performance. First, the welded and bolted plates are numerically modeled using Hypermesh pre-processing functions. Then, the boundary conditions are simulated by continuous variable stiffness elastic constraint experiments. Finally, the intrinsic vibration dynamic model of the four-sided simply supported plate and four-sided solidly supported plate is established using the modal superposition method. By analyzing the modal frequencies and vibration patterns, the following results are obtained. The connection method between the plate and the frame has a significant impact on the inherent vibration characteristics of the plate. The bolt connection will make the plate’s intrinsic vibration frequency higher than that of the welding method, but the effect on the plate’s intrinsic vibration pattern is more minor. At the same time, in order to verify the accuracy of the model, the actual modal vibration patterns and frequencies of the same proportion of plates in the modal test are compared with the results of modal vibration patterns and frequencies obtained by Ansys. The errors of the two dynamic model analytical methods are within 1% and 3%, respectively. This result verifies the accuracy of the dynamic model of the metal plate and shell structure under different connection methods.

Fabrication and mechanical properties of thermoplastic corrugated sandwich panel with enhanced face‐core interface

AbstractThermoplastic sandwich structures are widely utilized in engineering fields due to their high specific strength and stiffness, recyclability, and impact toughness. The face‐core interface strength is crucial to maximize the performance benefits of sandwich structures. Two sizes of corrugated sandwich panels with hot‐melt bonding and resistance welding connection methods were fabricated. The mechanical properties of sandwich panels were compared using a combination of experimental, numerical, and analytical investigation. Edgewise compression (EC) and 3‐point bending (3 PB) tests were conducted to obtain load–displacement curves and investigate different failure modes of sandwich panels. The peak edge compression and bending loads of the resistance welded structures were 42% and 92% higher, respectively, and the face‐core interface was always well‐connected compared to those of the hot‐melt bonding. The results indicate that the resistance welding method can be utilized as a core bonding technique for thermoplastic composite sandwich structures and has great potential for aerospace application.Highlights A method that includes hot‐melt bonding and resistance welding are develop to produce thermoplastic composite corrugated sandwich panels (TPC‐CSPs). The TPC‐CSPs fabricated by resistance welding exhibit superior interface connection performance compared to hot‐melt bonding and this method enhance the structural load bearing capacity. The numerical and analytical method were presented to investigate the failure model, which was consistent with the experimental results.

Effect of Welding Time Variation in Resistance Spot Welding on Mechanical Properties of Dissimilar Joints on Mild Steel and AISI 304 Stainless Steel

Resistance spot welding plays an important role in the automotive industry for working on car bodies or frames. Welding with two different steel materials is used in automotive structures. However, the low strength of the joints of different steel materials is a major problem, limiting the scope of its application. The quality of the welding connection Resistance spot welding is influenced by several factors, namely, time, welding current, and electrode pressure applied during welding and post-welding treatment. In this research, mild steel plate with AISI 304 stainless steel is welded by Resistance spot welding with different variations of welding time, material hardness and tensile testing that will be investigated. The results showed that the highest Rockwell Hardness time was obtained at a welding time variation of 8 seconds with a current of 6000 Ampere was 112.2 so the higher the welding time, the higher the hardness obtained. welding 8 seconds with a welding current of 6000 Ampere obtained a maximum tensile strength of 20.4 kgf/mm2 so the greater the welding current, the tensile strength will increase.

Hydrodynamic Load Effect on Composite Polymer Cold-Water Pipe Joint in Ocean Thermal Energy Conversion

The cold-water pipe in Ocean Thermal Energy Conversion (OTEC) is a very important part of the process of producing electrical energy. The cold-water pipe functions to convey cold water with a temperature of 5°C from a sea depth of >500 m to the sea surface. The cold water in the pipe is allowed to experience a temperature increase of <3°C so that it can be used to dilute the ammonia in the condenser. The use of polymer composites as cold-water pipe materials is a challenge because the hydrodynamic load from seawater currents fluctuates in a direction perpendicular to the position of the pipe. The pipe length reaches >500 m consisting of several pipes connected using the Friction Stir Welding method. This research was conducted to determine the effect of the hydrodynamic load of seawater currents on Friction Stir Welding (FSW) connections, the stress distribution in pipe joints, and the thickness of pipes that are safe to use as OTEC cold water pipes. In addition, simulations were carried out using Inventor software on pipes with a length of 500 m, a diameter of 4 m, and variations in thickness from 18 cm to 30 cm which produced von Mises yield stress and stress distribution at different joints at each pipe thickness. In pipes with a thickness of less than 20 cm, the stress and stress distribution are purely influenced by the hydrodynamic load of seawater currents. Meanwhile, in pipes with a thickness greater than 24 cm, the stress that occurs in the pipe is influenced by the current and weight of the pipe. In pipes with a thickness greater than 24 cm, the stress in the pipe is concentrated in the middle of the joint which is the critical part of the pipe and is the initial point of failure. It was found that at a pipe thickness of 22 cm, the stress was distributed almost evenly because the stress caused by seawater currents was reduced by the heavy load of the pipe. So, from the simulation of cold-water pipes with polymer composite materials that experience hydrodynamic loads from seawater currents varying in thickness from 16 cm to 30 cm, it is recommended to use a pipe thickness of 22 cm so that the pipe connection is safer as an ocean-based OTEC cold water pipe application.

Experimental and theoretical study on seismic behavior of a new UHPFRC sandwich wall and wall-wall joint

A new type of precast ultra-high performance concrete (UHPFRC) sandwich wall is proposed in this study. The proposed UHPFRC sandwich wall is composed of the UHPFRC layers, extruded polystyrene foam (XPS) board layer, and short UHPFRC columns connecting the UHPFRC layers. Compared with the traditional reinforced concrete wall, the UHPFRC sandwich wall possesses lower self-weight, less reinforcement, and higher strength. In addition, two types of wall-wall vertical joint connection methods, flexible cable connection and embedded steel plate welding connection, are proposed. The pseudo-static tests on five UHPFRC sandwich wall specimens were conducted to study the effects of UHPFRC layer thickness, reinforcement ratio, and width of edge solid area on the seismic behavior of the wall. Then, the seismic performance of different connection methods was studied by pseudo-static tests on two T-shaped UHPFRC sandwich wall-wall joint specimens. Test results demonstrate that the unreinforced UHPFRC sandwich wall, with 20–30 mm UHPFRC thickness and 150 mm edge solid area, showed excellent cracking resistance and seismic behavior. The cracking loads are more than 50% of the peak loads, and the bottom shear capacity to self-weight ratios are generally more than 35. The seismic behavior of the wall-wall joints connected by the flexible cable and embedded steel plate welding are both reliable. Finally, formulas for cracking and peak load of the UHPFRC sandwich wall are proposed and the fiber model is developed for analysis of the wall-wall joint, which is verified by the test results to be accurate and reasonable.

Cyclic behavior of dual-steel beam-to-column welded flange-bolted web connections

Cyclic loading tests on dual-steel beam-to-column welded flange-bolted web connections were conducted to quantify their moment resistance, plastic deformation and energy dissipation capacities. The test program consisted of five one-sided connection specimens, where Q355 grade beams and Q690 grade columns were used, to study the effects of beam-to-column welded flange connection details and panel zone shear strength on the connection seismic performance. Two types of welded connection details were considered; one was the traditional complete-joint-penetration (CJP) welded connections by use of backing bars, and the other type was those with the bottom backing bar further reinforced by a fillet weld. Three column web thicknesses were designed to arrive at strong, intermediate and weak panel zones, respectively. It was found that the CJP weld with the backing bar reinforced only under the bottom beam flange produced satisfactory performance and accommodated plastic rotations larger than 0.03 rad, while a maximum plastic rotation of 0.04 rad could be developed in the high-strength steel panel zone before fracture occurred. These results evidenced that those dual-steel connections could still sustain high seismic deformation demands.

The Effect of Variation of Bar Surface Chamfer Angle on Rotary Friction Welding Connections

This study aims to determine the effect of chamfer angle variations on flash, welding time, interface and hardness values at welded joints of similar materials. The method was used, with parameters of the rotational speed of 4.335 rpm, friction pressure of 0.5 MPa, forging pressure of 0.7 MPa, forging time of 10 seconds and chamfer angle variations of 0°, 15°, 30°, 45°. Then, the specimen result was tested using the projector profile, Non-Destructive Test (NDT), macro-observation, and Vicker test. The result showed that the greater the chamfer angle variation on the given bar surface, the smaller the size of the resulting flash. The smallest flash dimension was produced at a chamfer angle variation of 45°, with an average flash height of 1.03 mm, successfully reducing the flash height by 62% from variations without chamfer angles. Moreover, an average flash width of 0.26 mm reduced the flash width by 77% of the variation without a chamfer angle. Therefore, the greater the variation of the chamfer angle, the smaller the flash size and the more significant the variation of the chamfer angle, the longer the welding time. In the interface area, chamfer angle variations do not affect cracks and voids. The chamfer angle affects the average hardness value, where the more significant the chamfer angle, the more the hardness value is increased.

Experimental and numerical study on fatigue damage evolution of Q690D welding details

Steel structures are widely used in various types of structures, and welding details, which are fatigue-prone constructions, are typically utilized in steel constructions. In this study, regarding the high cycle fatigue performance and fatigue damage evolution behaviors of high strength steel welding details, experimental and numerical studies have been carried out on two typical types of Q690D high strength steel welding details, including butt-weld connections and cruciform load-carrying fillet weld (CLFW) connections. High cycle fatigue tests have been conducted, SN curves based on effective notch stress have been established and compared with the suggested curves in IIW specification, showing that FAT200 is more suitable for fatigue evaluation of high strength steel welding details. Fatigue damage evolution model and numerical simulation methods for Q690D welding details based on effective notch stress and continuum damage mechanic have been established and validated. Damage evolution analysis of welding details has been conducted based on the proposed numerical simulation method. The simulation method enables accurate characterization of fatigue damage locations.

A review of metal-to-plastic joinery in automotive manufacturing

Reducing weight and improving energy efficiency are key design goals in the automotive industryIn order to reduce the weight of the car body, engineers often use plastics in the parts of the car that require less strength. However, due to the difference in material properties, when using plastics to connect steel frames, there are disadvantages such as small interface area, large number of interfaces, and poor reliability of plastics, which may have a great impact on the safety of the car. Therefore, these plastic parts Joinery to the steel frame of the car needs careful consideration. Various methods, such as welding, bolt and nut connection, riveting, and crimping, were considered to connect plastic and metal in automobiles. This article first introduces the specific implementation of the joinery method between plastic and metal, and investigates their process difficulty, interface strength, vibration resistance and the least negligible cost. Discusses where these processes are suitable for use in the car, where they are currently used, and explores potential future developments.

Monitoring for fatigue crack geometry in orthotropic steel bridge decks by application of reflected Lamb waves

Orthotropic steel bridge decks (OSDs) have been widely used as a crucial load-bearing structures in long-span bridges,. However, the weld connections in OSDs are susceptible to fatigue crack initiation due to the high stress cycle caused by vehicle loads. Reflected Lamb waves have potential in the monitoring of crack geometry, and different sensor arrangements are employed for different crack types in OSDs. Three full-scale specimens were fabricated and tested with the recommended sensor arrangements to continuously monitor two types of cracks in tests. Finite element models were also established and verified by the experimental results. Parametric studies were conducted to investigate the effects of sensor arrangements, crack lengths and angles on monitoring results. A wavelet transform algorithm was applied to analyze reflected waves and extract standardized wave features, based on which the crack geometry was evaluated. The experimental results reveal that the standardized wave features from the reflected Lamb waves change significantly with the increase of fatigue life, indicating that the features are sensitive to fatigue crack growth. The simulation results reveal that the standardized wave features effected by crack geometry are positively correlated with projected crack lengths perpendicular to the direction of wave propagation. The optimal arrangements of wave sensors for crack monitoring at deck-to-rib connections are to place excitation and reception sensors at 200 mm and 60 mm from the welds at crack initiation plates, respectively; while for cracks at rib-to-floorbeam connections, excitation and reception sensors are located at 200 mm and 50 mm distant from the horizontal welds at cut-out, respectively, and all sensors are 50 mm distant from vertical welds.