Severe Loading Conditions Research Articles

Effects of propeller cavitation on ship propulsion performance in off-design operating conditions

The propeller cavitation is closely related with its hydrodynamic performance. When the propeller works in the cavitating flow, the propeller hydrodynamic performance, in terms of thrust and torque coefficients, is reduced due to the propeller cavitation. When the high-speed and high-power ship sails in adverse sea, the varying loads on propeller will cause severer cavitation on propeller. The reduction in propulsion performance caused by cavitation will further affect the propulsion system, impacting the ship sailing performance and safety. The VP1304 propeller cavitation CFD simulation are conducted to validate the CFD method. Furthermore, the influence of propeller advance ratio and cavitation numbers on the performance of low-speed high-power series propeller in cavitating flow are studied and illustrated. This influence of cavitation has also been transferred to the propulsion system and this process are calculated by the ship propulsion system numerical model. Additionally, the sailing performance of ship propulsion system under off-design conditions, where the cavitation is more likely to occur, has been investigated in this article. Under severe heavy load conditions, it can even result in a complete loss of propulsion capability, posing significant risks. Therefore, it is necessary to further optimize control strategies for the propulsion system to mitigate the hazards caused by cavitation.

Numerical study of steel beam to reinforce concrete column (RCC) connection with through-plate and buckling-restrained steel plates

This study examines the behavior and failure mechanisms of steel beam-to-reinforced concrete column connections with through-plate and buckling-restrained steel plates (BRSPs) configurations. These connections are critical components in composite steel and concrete structures, playing a vital role in force transfer and resistance to various loads, especially dynamic loads such as earthquakes. The primary objective of this study is to analyze the hysteresis behavior of these connections under cyclic loading using numerical analyses. Parametric models with varying BRSP thicknesses, ranging from 5 to 25 mm, were used to investigate their impact on hysteresis behavior and load-bearing capacity. The effects of different BRSP thicknesses on stress distribution and failure mechanisms were analyzed. The results from the parametric studies show that increasing the thickness of BRSPs improves the stress distribution in the beam-to-column connections. This improvement includes reduced stress concentration and enhanced uniformity of stress distribution, which can lead to reduced localized failures and increased overall connection stability. Numerical simulations indicate that the use of BRSPs (with a thickness of 15 and 17 mm) results in wider and more stable hysteresis loops, reflecting increased energy absorption capacity and improved deformation behavior of the connections under cyclic loading. The findings show that BRSPs can reduce failure concentration, increase flexural resistance, and prevent buckling in steel beams. These results underscore the importance of using BRSPs to enhance structural performance and mitigate potential failures under severe loading conditions.

Nonlinear time-dependent behavior of rheodictic polymers: A theoretical and experimental investigation

The present study examined the nonlinear time-dependent behavior of rheodictic polymers, a class of noncrosslinked materials that exhibit flow. Such behavior was addressed with extended Schapery's nonlinear viscoelastic model by introducing new physical quantities, i.e., the flow term Φflow and corresponding nonlinear shift parameter g2,flow. While Φflow portrays irrecoverable deformation, g2,flow depicts a nonlinear contribution to flow acceleration. This theory was accompanied by analytical and experimental methodologies for identifying all the parameters in the linear and nonlinear viscoelastic domains. Predictions of long-term time-dependent behavior (in shear) at various stress states show excellent agreement with the experimental data, i.e., within 5% error, obtained for polycarbonate at 130°C. Surprisingly, the newly introduced g2,flow indicates that flow retardation occurs with increasing stress, implying that a highly deformed entangled system hinders molecular reptation/disentanglement. Nevertheless, the proposed extension of Schapery's nonlinear viscoelastic model not only allows accurate predictions of the nonlinear time-dependent behavior of rheodictic polymers but also enables a detailed outlook on the underlying molecular mechanisms under severe environmental and loading conditions.

Conduction thermography for non-destructive assessment of fatigue cracks in metallic materials

Metallic materials are widely used in many applications of mechanical and aerospace engineering. Due to severe environmental and loading conditions, components and structures can experience cracking phenomena. In this regard, different non-destructive techniques were developed in the last years to detect and monitor cracks that can propagate during the actual loading conditions.This work deals with the application of the conduction thermography as a non-destructive technique for the offline control and inspection of different notched metallic specimens characterized by short fatigue cracks. The potentials of the technique have been demonstrated considering a low-cost set-up consisting of a power supply of low current and limited voltage, and a microbolometer sensor. Moreover, to further simplify the inspection, the specimens were not black coated. Quantitative results, in terms of crack lengths, have been obtained using a new procedure of data analysis and then compared to those provided by thermoelastic stress analysis, a well-established technique adopted for the detection and monitoring of cracks.

Microstructure and abnormal mechanical properties under the coupling effect of strain and temperature for friction-stir-welded joints of Al-Mg-Si alloy

In the fields of automotive engineering and shipbuilding, friction stir welding (FSW) is utilized for joining aluminum alloy structural components. However, the nugget zone (NZ) in FSW joints often exhibits anomalous mechanical properties, consequently diminishing the stability of the welded joints. Here, an NZ was subdivided into a high-strain nugget zone (HS-NZ) and a high-temperature nugget zone (HT-NZ). The anomalous mechanical properties of the Al-Mg-Si alloy HS-NZ were systematically investigated at welding speeds of 100 mm/min and 200 mm/min and rotational speeds of 600 rpm and 900 rpm. Compared to the HT-NZ, the average grain size of the HS-NZ reduced by a maximum of 3 μm, the density of geometrically necessary dislocations (GNDs) increased by a maximum of 0.26 ×1014 m−2, and the microhardness showed a maximum increase of 15 HV. However, its shear strength is lower than that of the HT-NZ, with a maximum decrease of 15 MPa, exhibiting an abnormal mechanical performance. The increase in the "soft-oriented" grains in the HS-NZ results in more localized stress concentration between "soft-oriented" and "hard-oriented" grains during the deformation, thereby providing a reasonable explanation for the observed reduction in shear strength in HS-NZ under severe loading conditions. The increase of "soft-oriented" grains is primarily attributed to the promotion of discontinuous dynamic recrystallization (DDRX) facilitated by the coupled effects of high temperature and high strain. The constructed mathematical model also illustrated the effect of the coupled temperature and strain fields on the abnormal shear strength.

Determination of the limits of operational loads of rubber shock absorbers during compression

Determining the limits of operational loads of rubber shock absorbers is an urgent task in the development of methods of non-destructive control of their condition. Therefore, the object of research is the influence of the limit values of the parameters of rubber shock absorbers during their static compression under harsh operating conditions. One of the most problematic issues is cylindrical shock absorbers with a form factor of less than 1.0. In the work, rubber shock absorbers of different hardness were used, which are model samples for tests of cylindrical shock absorbers with a form factor of 0.42, which were carried out on a laboratory stand. The study of compression process of rubber shock absorbers is an urgent task in modelling the conditions of their operation. The obtained results make it possible to simulate the most effective diagnostic parameter of rubber shock absorbers during compression and to establish its limit and permissible values. It has been established that different rubber hardnesses provide different compression rates, which can be used to study non-destructive testing of shock absorbers, especially under which conditions they can be used in practice. According to the indicators of relative deformation during compression, the use of rubber shock absorbers from the group of high hardness is recommended for more severe load conditions during exploitation. Soft and medium-hard rubbers are characterized by an increased relative deformation of the shock absorber's geometric size (height) during compression, which can lead to their destruction under increased loads. The obtained results on model samples can be checked on rubber shock absorbers manufactured in industrial conditions. The conducted research allows to create methods of choosing rubber shock absorbers for certain operating conditions depending on the coefficient of its shape. Limits of indicators simulating operating loads for different types of rubber shock absorbers have been established, which can be used when choosing a type of rubber for certain load conditions, and choosing a reinforcing material for the rubber array of the shock absorber and its shape.

A Meso-scale study to predict high-temperature behavior of concrete structures in a hygral-thermal-chemical-mechanical framework

Fire has become one of the common hazards that a concrete structure faces in today’s world. Considering the heterogeneity of concrete and the contrasting nature of the constituents at high temperatures (cement paste dehydrates and shrinks while aggregate expands in volume), the use of a homogeneous macroscopic model to predict concrete's thermo-mechanical performance is questionable. Therefore, a more realistic description of concrete (in terms of explicit consideration of coarse aggregate and cement mortar rather than homogenized concrete medium) is needed to characterize the behavior of a concrete structure under such severe loading conditions (e.g., fire). In fact, the performance of a macro-scale (meter size or higher) concrete structure is the coupled effect of the various physico-chemical processes that occur within its constituents at meso-scale, a scale (mm-cm scale size) where coarse aggregates are randomly distributed in a mortar paste medium. Therefore, it is required to develop a model that explicitly considers the constituents' contrasting nature and the different thermo-hygral-mechanical processes at the scale of occurrence of these processes. Hence, in this contribution, a meso-scale based model is developed in a coupled hygro-thermo-chemo-mechanical (HTCM) framework to investigate the effect of high temperature on the thermo-mechanical performance numerically (e.g., in terms of spalling, deformation, residual capacity, etc.) of fire-exposed plain and reinforced concrete structural elements (e.g., slab, beam, etc.). Simulated results and validation with experimental data (taken from the literature) highlight several crucial aspects related to obtaining a more precise residual capacity of a concrete structure, which is impossible to reproduce with a homogenized macroscopic model. The study highlights that the failing of random concrete parts at different times during high-temperature exposure can not be simulated with a homogenized assumption. Further, a mesoscopic model does not require transient creep strain to be specified explicitly. The primary influencing factors behind this transient creep strain, such as the different thermo-chemical and thermo-mechanical damage of the concrete constituents (cement paste, aggregate), thermal-incompatibility of the components and associated damages, etc., are implicitly taken into account in a meso-scale model.

Adaptive Control Approach for Accurate Current Sharing and Voltage Regulation in DC Microgrid Applications

A DC microgrid is an efficient way to combine diverse sources; conventional droop control is unable to achieve both accurate current sharing and required voltage regulation. This paper provides a new adaptive control approach for DC microgrid applications that satisfies both accurate current sharing and appropriate voltage regulation depending on the loading state. As the load increases in parallel, so do the output currents of the distributed generating units, and correct current sharing is necessary under severe load conditions. The suggested control approach raises the equivalent droop gains as the load level increases in parallel and provides accurate current sharing. The droop parameters were checked online and changed using the principal current sharing loops to reduce the variation in load current sharing, and the second loop also transferred the droop lines to eliminate DC microgrid bus voltage fluctuation in the adaptive droop controller, which is different and inventive. The proposed algorithm is tested using a variety of input voltages and load resistances. This work assesses the performance and stability of the suggested method using a linearized model and verifies the results using an acceptable model created in MATLAB/SIMULINK Software Version 9.3 and using Real-Time Simulation Fundamentals and hardware-based experimentation.

Features of the experimental evaluation of the fatigue resistance characteristics of power lugs

The features of the fatigue strength of the lugs in different zones of the cycle asymmetry coefficient are considered. It is shown that the most severe conditions of variable loading of the lugs correspond to a cycle asymmetry coefficient from 0.1 to 0.2. Formulas have been obtained to clarify the statistical assessment of the durability of symmetrical lug samples when, during their fatigue testing, destruction occurs on only one side. Recommendations are given for the selection of accelerated test modes with forced loading and for comparative tests at the same stress amplitude level.

Fracture behaviour assessment of high-performance fibre-reinforced concrete at high strain rates using interpretable modelling approaches

High-performance fibre-reinforced concrete (HPFRC), a type of cementitious composite material known for its exceptional mechanical performance, has widespread applications in structures exposed to severe dynamic loading conditions. However, understanding nonlinear HPFRC fracture behaviour, particularly under high strain rates, remains challenging given the complexities of assessment procedures and cost-intensive nature of experiments. This study presents an interpretable framework for modelling and analysing HPFRC fracture strength at high strain rates. A wide range of machine learning methods, including ensemble techniques, were employed to capture multivariate effects of eight essential input features (e.g., mortar compressive strength, fibre physical and mechanical properties, cross-sectional area, and strain rate) on fracture strength response. To assess the derived models, a novel evaluation procedure was proposed involving a data-based analysis, employing established metrics (i.e., coefficient of determination, root mean squared error, and mean absolute error via K-fold cross-validation) and a domain experts-involved evaluation utilising global sensitivity analysis to discern first-order and higher-order interactions among input factors. The proposed approach efficiently yielded both quantitative and qualitative insights into crucial input factors governing HPFRC fracture strength with limited experimental data. The obtained findings highlight the significance of multivariate effects, such as the interaction between strain rate and fibre tensile strength, and between fibre volume and fibre diameter, on fracture behaviour. The proposed interpretable framework aims to provide a powerful tool for proactive material failure analysis by understanding fracture behaviour and identifying potential weak and strong interactions among input factors of HPFRC-based samples. Moreover, the utilisation of the proposed approach enables researchers and civil engineers to efficiently focus on the most critical input parameters during the early design stage and ensuring the structural integrity and safety of HPFRC-based constructions.

Designing hydrogen-free diamond like multilayer carbon coatings for superior mechanical and tribological performance

Diamond like carbon (DLC) coatings are extensively employed for their outstanding mechanical and tribological properties. To overcome the inherent high residual stress, therefore brittleness, DLC coatings with multilayer architecture were developed in the form of stacking alternate hard and soft layers to avoid premature failure under severe loading conditions. The current study was designed to investigate the impact of bilayer thickness (hard & soft) on wear of multilayer DLC particularly at high contact stress (2.0 GPa, 2.7 GPa, 3.0 GPa, 3.4 GPa). Seven DLC multilayer (1:1 bilayer ratio) samples with 1, 2, 5, 10, 20, 40, 80 bilayers were deposited on 440C steel and the overall coating thickness was mainatined at ∼1 µm. Moreover, the bilayer thickness effect was determined on mechanical, scratch adhesion and structural properties. Transmission electron microscope (TEM) was used to visualize discrete hard and soft layers in 80 bilayers (∼6 nm thin layer). G peak suppression and ID/IG increment were observed with reduction in bilayer thickness. Hardness, modulus, elastic strain to failure (H/E), plastic deformation resistance (H3/E2) and residual stresses showed an inverse relation with bilayer thickness. Furthermore, micro scratch adhesion decreases with layer thickness reduction. Only 100 nm and above bilayer thickness samples (1, 2, 5, 10 bilayers) could survive under high contact stress while the other three (20, 40, 80 bilayers) showed brittle failure using pin-on-disc tribometer. Additionally, 10 bilayers (100 nm thickness) produced the minimum wear (∼7.9 ×10−8 mm3/Nm) at 80 N.

Study on Various Position Sensing Technologies in Tractor Hitch Application

Conventionally, In the tractors, hitch position is obtained using a contact-based position sensor, the sensor is attached to the rockshaft mechanically with gears or linkages. In this arrangement, there are incidences of failures when working with heavy implements, as rockshaft is under severe loading conditions which tends to induce cracks or failures in sensor mechanical linkages mounting area. This results in machine downtime and rockshaft repair costs to the customer. These mounting threads in hardened Rockshaft reduce material strength which impacts the lifting capacity. There is associated difficulty at assembly line and further during maintenance for linkage installation and adjustments. Also, over the period, linkages develop a play at joints due to the friction. In the present work, we are sensing the Hitch position with contactless sensor technology. A contactless Hall effect sensor is selected, and proto setup has been designed to measure the hitch position by integrating the sensor and target. The prototype consists of a fixed Sensor and a rotating metal (ferromagnetic) piece placed inside a 3D printed casing. The profile of metal piece is such that when it is rotated about the axis, the distance between Sensor and metal piece changes gradually. This causes different output voltage at different amount of rotation in metal piece. Results from manual bench testing show that the concept is working. The sensor voltage output varies according to the hitch position in the bench setup. A high voltage value when metal piece is nearer to magnet and low value when its farther. A future step is to automate this setup on a tractor to remove errors due to manual rotation. This would be an enabler to analyze the sensor behaviors like hysteresis, repeatability, linearity more accurately.

Performance analysis of rolling multi-lug cable-strut joints with bearings under extreme loads

The tensioning process in the traditional cable strut joint leads to significant prestress loss, thereby adversely affecting the structure's performance after tension forming. This paper proposes a rolling multi-lug cable-strut joint with bearings. To investigate the rate of prestress loss in the new tension joint, we conduct testing of joint performance in a dome model experiment. The mechanical properties of the joint in the overall structure of the cable dome under ultimate load are analyzed. The investigation shows that the new joint design significantly reduces prestress loss by more than 10% compared to traditional cable support joints. Afterward, the theoretical model of the RMCS joint is proposed by analyzing the force state and deformation of the dome structure space. The test data verify the model. Based on this theoretical model, the influence of prestress loss of different levels was studied. Under severe loading conditions, the path of force transfer through the joint is efficient and can prevent large fluctuations in the cable force of the structure. The cable force on both sides of the joint still fluctuates at the same frequency even under extreme loading of the dome structure.

Structural sensitivity to reliability of flexible AMOLED modules using mechanical simulation and machine learning

The flexibility and durability of flexible AMOLEDs are considered mutually exclusive, and their structural integrity under severe load conditions can be attained by minimizing the trade-off between these two properties. In this regard, the thickness and elastic modulus of the plastic films comprising flexible AMOLEDs are crucial design variables that determine their reliability. This study proposes a method for predicting the performance sensitivity of an AMOLED to its flexibility and durability using mechanical simulation and machine learning. A combination of 1000 thicknesses and elastic moduli, generated by Latin hypercube sampling, was used for the mechanical simulation. The results of the mechanical simulation were used to train various machine-learning algorithms, and the performance was evaluated using leave-one-out cross-validation (LOOCV). The CatBoost algorithm, which produced the best accuracy, and Kernel Shapley Additive Explanations (SHAP), were utilized to represent the sensitivity of the thickness and elastic modulus and their mutual exclusiveness is experimentally verified. These results will provide crucial information for the optimal design of flexible AMOLED modules.

Toward a continuum description of lubrication in highly pressurized nanometer-wide constrictions: The importance of accurate slip laws.

The Reynolds lubrication equation (RLE) is widely used to design sliding contacts in mechanical machinery. While providing an excellent description of hydrodynamic lubrication, friction in boundary lubrication regions is usually considered by empirical laws, because continuum theories are expected to fail for lubricant film heights h0 ≪ 10 nm, especially in highly loaded tribosystems with normal pressures pn ≫ 0.1 GPa. Here, the performance of RLEs is validated by molecular dynamics simulations of pressurized (with pn = 0.2 to 1 GPa) hexadecane in a gold converging-diverging channel with minimum gap heights h0 = 1.4 to 9.7 nm. For pn ≤ 0.4 GPa and h0 ≥ 5 nm, agreement with the RLE requires accurate constitutive laws for pressure-dependent density and viscosity. An additional nonlinear wall slip law relating wall slip velocities to local shear stresses extends the RLE's validity to even the most severe loading condition pn = 1 GPa and h0 = 1.4 nm. Our results demonstrate an innovative route for continuum modeling of highly loaded tribological contacts under boundary lubrication.

Quantitative assessment for tooth crack of the sun gear in a planetary gearbox

The sun gear in a planetary gearbox is prone to generate tooth crack due to its much more severe load conditions than other gears. The cracked sun gear will evolve into distinct tooth breakages and thus may deteriorate the operation status and even cause catastrophic loss of the whole transmission system. To avoid tooth crack induced malfunction of the planetary gearbox, the tooth crack of sun gear should be accurately identified during the early stage. Therefore, a novelty quantitative assessment methodology for tooth crack damage is proposed, which is a mathematical model for crack propagation of the sun gear in planetary gearboxes based on vibration acceleration signal. Firstly, the quantitative relationship between the crack propagation parameters along the gear thickness and width directions and the time-varying mesh stiffness is analytically formulated. The analytical time-varying mesh stiffness formulation is incorporated into a translational–torsional dynamic model to reveal the effects of crack propagation on the vibration signal of internal and external meshing pairs in the planetary gearbox. Secondly, a quantitative mapping function is established by taking the cracked section area as the variable and the residual of the summed envelope spectrum amplitude of the vibration acceleration signal as the assessment index. Finally, a numerical simulation as well as an experimental test is conducted and compared to verify the correctness of the proposed assessment methodology. We believe that the established model and the corresponding index provide a physically intuitive yet mathematically quantitative reference for diagnosing tooth crack in planetary gearboxes.

Static and dynamic performance of different concrete mixtures for the protection of aircraft shelters

Concrete is the most significant construction material in the world. However, extreme static and dynamic loads placed on infrastructure in recent decades have led to structurally catastrophic disasters. In addition, recent weapons can significantly impact the safety of humans and infrastructures. Newly developed concrete shields are designed to protect against severe loading conditions such as impact loads. Therefore, due to the rapid progress in weapons production, such as projectiles and bombs, there is a critical need to protect aviation buildings and aircraft shelters from such destructive impacts. In this study, the static and dynamic performance of concrete shields produced by nationally available magnetite, hematite, graphite, steel fibers, and steel mesh constituents were evaluated. Test results showed that implementing graphite, hematite, and magnetite powder in concrete shelters’ production slightly decreased the static behaviour of produced mixtures. On the other hand, superior impact resistance was achieved by incorporating steel fibers and steel mesh in aircraft concrete shields.

Determination of critical state line (CSL) for silty-sandy iron ore tailings subjected to low-high confining pressures

The disposal of filtered tailings in high dry stacks can induce particle breakage, changing the material's behaviour during the structure's lifetime. The grading changes influence material properties at the critical state, and this is not mature for intermediate artificial soils (tailings) in a broad range of confining pressures. In this paper, it aims to describe the behaviour of iron ore tailings in a spectrum of confining pressures broader than the reported in previous studies. A series of consolidated drained (CD) triaxial tests was carried out with confining pressures ranging from 0.075 MPa to 120 MPa. These results show that the amount of breakage plays an essential role in the response of iron ore tailings. The existence of curved critical state line (CSL) in both specific volume (ν)–logarithm of mean effective stress (p′) and deviatoric stress (q)–mean effective stress (p′) planes, and different responses in the deviatoric stress–axial strain–volumetric strain curves were verified. An inverse S-shaped equation was proposed to represent the silty-sandy tailings' behaviour up to high pressures on ν–lnp′ plane. The proposed equation provides a basis for enhancing constitutive models and considers the evolution of the grading up to severe loading conditions. The adjustment considered three regions with different responses associated with particle breakage at different pressure levels.

A New Geometrical Design to Overcome the Asymmetric Pressure Problem and the Resulting Response of Rotor-Bearing System to Unbalance Excitation

Improving the bearing design helps in reducing the negative consequences related to errors in installation, manufacturing, deflections under severe loading conditions, progressive wear of machine elements, and many other aspects. One of the methods of such a design improvement effort is changing the bearing profile along the bearing width to compensate for the reduction in the geometrical gap between the shaft and the bearing inner surface due to the aforementioned causes. Since in all rotating machinery, unbalance usually exists at some level, this paper deals with the response of this modified bearing to unbalanced excitation to evaluate the effectiveness of such geometrical design on the dynamic characteristics of the rotor-bearing system. The numerical solution is performed using the finite difference method by assuming Reynolds boundary conditions to determine the cavitation limits, and the 4th-order Range-Kutta method is used to determine the time responses resulting from the unbalance excitation. The time responses to this type of excitation show that the rotor-bearing with the improved geometrical design is more stable, particularly at high speeds. In addition, this modification leads to an improvement in the lubricant layer thickness and the reduction in the levels of the generated pressure between the surfaces despite the presence of large deviations from the perfectly aligned bearing system. Furthermore, the suggested geometrical design overcomes the problem of asymmetricity in the pressure field resulting from the shaft deviation to a large extent. The results of this work (the enhancement in the level of the film thickness and the improvement in the dynamic response of the system as well as the reduction of the maximum pressure value) extend the range of misalignment in which the rotor bearing systems can operate safely which represents a significant step in designing the rotor-bearing system.

Fatigue Performance of Rib-to-Deck Double-Sided Weld Joint of Orthotropic Steel Deck on Plate Girder Railway Bridges

This research work presents the stress behavior of rib-deck weld joints in Orthotropic Steel Deck (OSD) railway bridges. It is essential to determine the most vulnerable load mode of the wheels for fatigue failure of OSD bridges and to improve the fatigue resistance of the welded rib-deck connection. Fatigue performance largely depends on the weld stress. Double-sided welds for rib-deck welds improve fatigue performance. The fatigue behavior of the rib-deck double-sided weld joint has been compared with the single-sided one. This study used Abaqus software to create the global shell model and the solid submodel of the OSD. The results of the structural stress-based finite element analysis indicated that when the center line of the front axle pair of a locomotive coincides with the center line of the midspan of the bridge, the most severe loading condition occurs. The rib near the main girder experiences the maximum structural stress in the weld toe of the rib-deck joint. Moreover, the rib-deck double-sided weld joints have 43.7% less structural stress compared to single-sided weld joints at the root of the weld, and this improves the performance during fatigue of OSDs.