Loading Conditions Research Articles

Experimental characterization and numerical modeling of a frequency-independent viscoelastic damper

Conventional viscoelastic dampers (VED) exhibit significant frequency dependency, leading to variability in stiffness and damping properties at different excitation frequencies, which introduces uncertainties in their design and application in practical engineering. This study addresses this issue by developing a frequency-independent VED through comprehensive experimental characterization and numerical modeling. Four full-scale VEDs were designed and manufactured to explore its mechanical behavior. Cyclic loading tests were carried out under various loading conditions, including different strain amplitudes, loading frequencies, ambient temperatures, and low-cycle fatigue tests. Then, a frequency-independent mechanical model is proposed by combining an energy dissipation element with a nonlinear stiffness element in parallel. Finally, nonlinear dynamic time-history analyses were conducted on a steel frame with and without the VEDs at various ambient temperatures. The experimental results show that the developed VEDs maintain consistent hysteretic behavior across a range of frequencies, exhibit high mechanical stability under varying strain amplitudes and temperatures, and possess excellent recoverability after low-cycle fatigue test. The frequency-independent mechanical model developed in this study accurately simulates the hysteretic response of the developed VEDs, validating its applicability through experimental data. Seismic response analyses demonstrate considerable mitigations in inter-story drift ratios and residual inter-story drift ratios compared to the frame without dampers. These findings highlight the reliability and effectiveness of frequency-independent VEDs in structural vibration control, offering a promising solution for seismic performance enhancement.

Impact of various fibers on mode I, III and I/III fracture toughness in slag, fly Ash, and silica fume-based geopolymer concrete using edge-notched disc bend specimen

There is ongoing research aimed at developing cement-free concrete that not only exhibits enhanced mechanical properties but also incorporates environmentally sustainable materials. Geopolymer represents a novel inorganic cementitious material recently developed, which facilitates utilising resources derived from solid waste from industrial operations. Geopolymer is considered an ecologically sustainable substitute for Ordinary Portland cement. It significantly reduces energy usage and minimizes carbon dioxide emissions, contributing to environmental sustainability. This study investigates the combined influence of granulated blast furnace slag, fly ash and silica fume on geopolymer concrete (GC) fracture resistance. This research aims to assess the fracture toughness of GC under modes I, III, and I/III loading conditions. Four distinct fiber types, comprising both short and long steel fibers and polypropylene fibers at 1.5 % dosage, were utilized to mitigate brittleness and enhance the ductility of the material. In addition, the microstructure of GC was analysed using X-ray diffraction and scanning electron microscopy. Findings reveal that the inclusion of short and long polypropylene fibers in GC increased mode I fracture toughness by 20.98 % and 29.62 %, respectively, compared to the fiber-free specimen, with long fiber showing superior performance due to its enhanced crack-bridging ability. Steel fibers provided a more pronounced improvement, with short and long fibers increasing mode I fracture toughness by 77.77 % and 109.87 %, respectively, attributed to their capacity to hinder crack propagation and enhance fracture toughness. The long fibers exhibited an excellent fracture resistance than the short fibers and mode III is more critical than the mode I loading.

A modified Johnson-Cook constitutive model of Inconel 690 weld overlay taking into account the strain rate softening effect

Precise material constitutive models are essential for finite element (FE) cutting simulation and analytical calculations of cutting mechanics. In this work, a split Hopkinson pressure bar (SHPB) equipment was employed to investigate the dynamic mechanical behavior of Inconel 690 weld overlay with a wide range of temperatures (20℃, 200℃, 400℃, 600℃, and 800℃) and strain rates (5000s-1, 7500s-1, 10,000s-1, and 12,500s-1). Based on the material flow characteristics at different loading conditions, a modified Johnson-Cook (JC) constitutive model was established, which takes into account the strain rate softening effect at high strain rates and the softening behavior induced by the competition between work hardening and dynamic recovery at large strains. Compared with the original JC constitutive model, the modified constitutive model can provide a closer correspondence between the predicted flow stresses and experimental data. The modified material constitutive model was introduced into FE simulation for orthogonal cutting of Inconel 690 weld overlay. The results indicate that the average prediction errors for the main cutting force and thrust force are 6.38% and 11.38%, respectively, validating the applicability and reliability of the modified JC constitutive model for cutting simulation applications. This study can provide a mechanical foundation for FE analysis in high-speed cutting of Inconel 690 weld overlay, which is conducive to optimizing cutting parameters, reducing machining costs, and enhancing production efficiency in practical industrial manufacturing.

The roles of loading rate and temperature during shear-band-to-crack transition (SCT) in bulk metallic glasses: A study of quasi-static and dynamic shearing performances at ambient and cryogenic temperatures

The concomitant of relatively ductile-like shear banding and brittle-like fracture in metallic glasses makes their failure origin, i.e., how shear bands developing into cracks, a concerned issue to reveal the unique properties of the amorphous metals. Such shear-band-to-crack transition (SCT) is prominently influenced by loading rate and temperature, whereas their roles are usually ambiguous. In this paper, serial quasi-static and dynamic tests at ambient and cryogenic temperatures were performed to clarify the roles of strain rate and temperature during SCT in a Zr-based bulk metallic glass (BMG) by an electronic testing machine and a modified split Hopkinson pressure bar (SHPB) system, respectively. Strain rates were set from 10−3 s−1 to 103 s−1 and temperatures were set from 173 K to 293 K. In-situ and post-fracture SCT patterns have been captured by high-speed photographing and scan electronic microscopy (SEM), which show a strong relevance to shear-band decohesion. Comparisons between SCT patterns under various loading conditions have clarified that loading rate controls decohesion distribution while temperature controls decohesion resistance. A decohesion-tendency ratio of applied energy to critical decohesion resistance is established from an energy-based view, and rate and temperature dependence of the ratio is discussed to figure out how these two effects determining different decohesion behavior and subsequent SCT patterns in BMGs.

Parametric assessment of new O-ring bracing performance under progressive collapse using nonlinear analysis

Progressive collapse poses a significant threat to the structural integrity of buildings under extreme loading conditions, necessitating robust design strategies to mitigate its effects. This paper extends prior research by the same authors on the performance of O-ring bracing during progressive collapse in comparison with other bracing systems. The primary objective is to investigate various design parameters and configurations that optimize the performance of O-ring bracing systems under progressive collapse scenarios through a comprehensive parametric assessment. Nonlinear finite element analysis is employed to evaluate different design parameters, including the size, shape, orientation, and strength of O-ring braced sections, and connection detailing. These factors are assessed for their influence on structural strength, stiffness, and ductility. The parametric study identifies configurations that significantly enhance structural resilience, providing recommendations for future designs aimed at preventing progressive collapse in O-ring braced frames. Data AvailabilityAll data is available from the Authors upon reasonable request.

Crystal plasticity based investigation of the effects of additive manufactured voids on the strain localization behaviour of Ti-6Al-4V

The presence of defects produced by additive manufactured (AM) processes in structural Ti alloys such as Ti-6Al-4V is known to have serious implications on the deformation and fatigue behaviour of engineering components. However, there is little understanding about the localised plastic deformation patterns that develop around AM defects, and the associated local conditions that could lead to the nucleation of micro-cracks under creep loading conditions. In this work, the effects of the morphology and volume fraction of AM defects and temperature on the strain localization behaviour around such defects in Ti-6Al-4V will be addressed. To that purpose, a novel rate-dependent crystal plasticity formulation is proposed to describe the mechanical behaviour of the alloy’s predominant α′(HCP)-phase. Representative volume elements (RVEs) of the AM produced microstructures are digitally reconstructed from EBSD orientation maps obtained on planes perpendicular and transversal to the microstructure’s AM growth direction. Calibration of the single crystal model for the α′-phase is carried out from macroscopic uniaxial tensile data from polycrystalline AM specimens at different strain rates and temperatures and published creep data.Furthermore, RVEs containing AM defects of different morphologies and volume fractions are relied upon to investigate the strain localization behaviour around the defects under uniaxial loading at ambient and high temperatures. It is found that the extent of the localised accumulated plastic strain around defects depends greatly on whether the voids surface are smooth or have sharp corners, with the latter being associated with more severe localisation patterns. Moreover, a numerical investigation into the crack initiation behaviour of AM Ti-6Al-4V under uniaxial creep loading at 450 ° C revealed that the development of the local conditions suitable for the nucleation of creep damage/micro-cracks is accelerated in the presence of typical AM defects, and the extent of that acceleration depends strongly on their morphology. An AM defect shape parameter is introduced to quantify the way their morphology affect the time for creep crack initiation/damage.

Optimal DSSC’s deployment in power system using PSO

Owing to the high cost of installation and operation, distributed flexible AC transmission system (FACTS) technology gives opportunity to provide cost-effective solution in power system operation and control. A distributed static series compensator (DSSC) is a series FACTS device and it is placed equidistantly placed on the existing line to vary the line current. Active power can be controlled in the line with the help of DSSC. This paper presents DSSC for active power flow control to enhance system loadability index and to minimize reactive power generation by generators. Since DSSC is of low power. a small value of reactance is emulated in the line. Large number of DSSC’s are distributed along the transmission line at regular intervals to realize considerable change in the current. A particle swarm optimization is implemented to determine DSSC’s emulated reactance optimally. In this condition, all the lines flowing power in their limits with increased loading condition. Maximum system loadability index is evaluated by employing optimal number of DSSC’s on the line. A multiobjective problem is formulated. One objective function is formed such that no line would become overloaded even when loading is increased. Other objective is formulated to minimize reactive power generation by generators. A compromise solution is investigated for optimally connected of DSSC devices to achieve both the objective functions. IEEE 14 bus system is taken for MATLAB simulation of DSSC compensated system.

Assess seismic resilience of unreinforced stone loess cave retrofitted with composite materials by shaking table tests

Unreinforced masonry (URM) structures have consistently suffered significant seismic damage in past earthquake events, leading to considerable losses in both life and property. Unreinforced stone loess cave (URSLC), a type of URM structure, are commonly used in the loess regions of northwestern China due to their affordability for low-income populations. Developing cost-effective and easily implementable reinforcement technologies to enhance the seismic performance of URSLC is therefore critical. In this study, a series of shake table tests were conducted to improve the strength and ductility of URSLC. Initially, the unreinforced structure was subjected to six progressively intense bidirectional seismic excitations, driving the structure to near-collapse. Subsequently, the damaged structure was retrofitted using composite materials, including steel bar/wire mesh mortar, steel belts, and epoxy resin. To compare the performance, a shaking table test was repeated on the retrofitted structure using the same seismic input as the initial test. Throughout the experiments, the damage progression, crack development, and failure characteristics of both the unreinforced and reinforced specimens were meticulously recorded. Additionally, dynamic properties before and after reinforcement were analyzed to assess the effectiveness of the retrofitting. The results demonstrated that the composite materials provided a strong bond between the stone layers and reinforcement, significantly improving the seismic resistance of the damaged loess caves. Moreover, the use of these materials was found to be both efficient and economical in enhancing the structural performance—particularly in terms of strength, stiffness, and damage tolerance. This study confirms that composite reinforcement can significantly improve the safety of masonry buildings, even under severe seismic loading conditions.

Dynamic response and constitutive model for coal-rock composite material subjected to impact loading

Comprehensive understanding related to the dynamic responses of the composite materials is critical to prevent natural disasters in underground engineering and mining activities. For this reason, experimental studies were undertaken using dynamic impact tests at different strain rates to explore the failure mechanism using split Hopkinson pressure bar (SHPB) system and Digital Image Correlation (DIC) on composite materials; coal-rock (C-R) and rock-coal (R-C). These results suggest a linear correlation between dissipative energy and fractal dimensions. In addition, they suggest cracks that develop predominantly on the coal side have a dominant influence on the failure process that could be attributed to the interface effects. The damage evolution was established assuming elastic conditions using a three-dimensional coupled FDM-DEM numerical simulation system. Anumerical approach is also developed for interpreting failure mechanism of the composite material based on the fabric tensor and strain energy density. Finally, a constitutiverelationshipis established considering strain rate effect and damage evolution using series element studies. There is a good agreement between the experimental and numerical results, providing justification to the proposed constitutive relationship. The numerical approach in this study is promising for assessing the performance of composite materialstaking account of dynamic loading conditions.

Investigating the Dynamic Behavior and Tensile Properties of Coal Gangue Shotcrete Under Impact Loading Conditions SHPB Device

Shotcrete is the primary support material for coal mine tunnel linings and is often subjected to dynamic loads such as blasting and impact. To promote the resource utilization of coal gangue (CG), this study incorporated it into shotcrete and investigated the dynamic mechanical properties of coal gangue shotcrete (CGSC) at different coal gangue aggregate (CGA) replacement ratios. Impact tensile splitting tests were conducted using a split Hopkinson pressure bar (SHPB) device, and the specimen failure process was recorded with a high-speed camera. The results showed that the dynamic tensile splitting strength (DSTS) and energy absorption of CGSC exhibit a significant strain rate effect, with the strain rate sensitivity of DSTS decreasing as the CGA replacement ratio increases. As the strain rate increases, the elastic limit stress of the specimens rises, and the failure mode tends to become more fragmented. Based on energy theory, this paper establishes a dynamic tensile splitting strength model for CGSC, providing theoretical support for its application in engineering.

Estimation of undrained shear strength of soft clay during surcharge or vacuum preloading

Preloading using either vacuum or fill surcharge is an effective method for the treatment of very soft saturated clay. The preloading will reduce the water content and increase the shear strength of soil. However, when the soil to be treated is very soft, it is difficult to take soil samples for laboratory tests or carry out in situ tests to determine the soil properties including shear strength. Therefore, there is a need to develop an analytical method to estimate the shear strength during preloading. In this paper, a simple correlation among settlement, water content and undrained shear strength using critical state theory is proposed for saturated soil under one-dimensional loading condition to allow the undrained shear strength variation of the soil to be estimated during preloading without testing. Laboratory model test and field monitoring data are used to verify the validity of this method and the proposed correlation is effective to be used as rough estimations on the undrained shear strength of soft clay.

Dynamic Analysis of Soil-Structure Interaction in Earthquake-Prone Areas

This study used a thorough experimental method to examine the dynamic interaction between soil and structures in earthquake-prone locations. The study challenge concentrated on how different soil types and configurations influence the diversity of structural reactions under seismic loading conditions. The research utilized a mixed methods approach, which involved quantitatively analyzing soil parameters and assessing structure dynamics. The methods employed included the creation of scaled replicas depicting common architectural structures situated on various soil types, including sandy, clayey, and mixed compositions. We used high-precision sensors to record ground motion characteristics such as Acceleration, velocity, and Displacement. The data was then evaluated using statistical methods such as ANOVA and regression analysis. The results revealed substantial differences in the structural reaction based on the type of soil and the parameters of the structure. Structures built on sandy soils saw greater peak accelerations (up to 0.170 g) but smaller displacements. On the other hand, structures on clayey soils had moderate accelerations (up to 0.140 g) but had bigger inter-story drifts. The varied soil layers, ranging from 1.500 Hz to 1.780 Hz, influenced the natural frequencies of the buildings. The damping ratios ranged from 5.000% to 7.800%, indicating that structural damping effectively reduces seismic forces. The results emphasized the critical importance of the interaction between soil and structures in seismic design and the necessity for customized engineering solutions based on the individual soil conditions at the site. Suggested measures include improving methods for soil characterization, optimizing structural dynamics using cutting-edge dampening technologies, and upgrading seismic design codes to enhance the ability of structures to withstand earthquakes in places prone to seismic activity.

Modeling linear and nonlinear viscoelastic oscillatory rheometric stress-strain hysteresis of asphalt binders

AbstractUnderstanding the complex stress-strain hysteresis behavior of asphalt binders under varied conditions is critical for optimizing pavement performance. This study addresses the challenge by analyzing and modeling asphalt binder responses in oscillating shear mode across different aging states (unaged, short-term aged, and long-term aged), stretch amplitudes, frequencies, and temperatures. Fifty-three stress-strain hysteresis loops were meticulously analyzed, revealing distinct stress paths relative to applied stretch levels. A nine-parameter parallel rheological framework model was developed, integrating a four-parameter eight-chain (FEC) hyperelastic model in one network and a FEC hyperelastic model with a linear viscoelastic flow element in series in another. This constitutive model was implemented in LS-DYNA finite element simulations to predict experimentally-measured stress-strain hysteresis loops accurately. The research demonstrates the model’s capability to simulate both linear and nonlinear viscoelastic responses of asphalt binders across a wide range of environmental and loading conditions. This approach significantly enhances our ability to capture and understand the stress-strain behavior critical for asphalt pavement durability and performance optimization.

Regulating Li2S Deposition and Accelerating Conversion Kinetics through Intracavity ZnS toward Low-Temperature Lithium-Sulfur Batteries.

The uncontrolled deposition behavior and sluggish conversion kinetics of the discharging product (solid Li2S) severely deteriorate the electrochemical performance of lithium-sulfur (Li-S) batteries, especially under high S loading and low-temperature conditions. Herein, a multifunctional S cathode host consisting of ZnS nanoparticles (NPs) confined in hollow porous carbon spheres (ZnS@HPCS) is synthesized via a unique capillary force-driven melting-diffusion strategy. The porous carbon shell of ZnS@HPCS provides a space-confined reservoir for soluble polysulfides and solid Li2S, while the intracavity ZnS NPs trap polysulfides, induce Li2S inside deposition, and accelerate conversion kinetics. Thus, Li-S batteries with ZnS@HPCS-S cathodes exhibit excellent electrochemical performance at both room and low temperatures (-40 °C) and high reversible capacities under high S loading (5.2 mg cm-2). Furthermore, Li2S nucleation/deposition, in situ Raman, and theoretical analyses reveal the underlying mechanism. This work offers fundamental insights into regulating Li2S deposition and designing S hosts for high-performance Li-S batteries.

Optimizing superelastic shape-memory alloy fibers for enhancing the pullout performance in engineered cementitious composites

Abstract This study explores the effect of integrated superelastic shape-memory alloy fibers (SMAFs) on the mechanical performance of engineered cementitious composites (ECCs). Various SMAF configurations – linear-shaped SMAFs (LS-SMAFs), hook-shaped SMAFs (HS-SMAFs), and indented-shaped SMAFs (IS-SMAFs) – with diameters of 0.8 and 1.0 mm were incorporated into ECC matrices, and surface texturization was achieved through abrasive paper treatment. Their mechanical properties were assessed through single fiber pullout tests on ECC mixtures containing 1.5 and 2.0% polyvinyl alcohol (PVA), subjected to both monotonic and cyclic loading conditions. Qualitative analysis, employing scanning electron microscopy, demonstrated that the IS-SMAF configuration provided superior mechanical interlocking and fiber–matrix adhesion, with a distinct flag shape observed during tensile testing. Quantitative data indicated that IS-SMAFs significantly improved the tensile strength and pullout resistance, with slip distances of ≥5 mm and average pullout loads ranging from 263 to 403 N. LS-SMAFs demonstrated better performance compared to HS-SMAFs and LS-SMAFs in terms of tensile and pullout characteristics. Additionally, ECCs with increased PVA content exhibited enhanced withdrawal performance. Thermogravimetry analysis and X-ray diffraction provided insights into the high-temperature stability and crystalline structure of the composites. These results underscore the effectiveness of IS-SMAFs in enhancing ECC properties, offering significant implications for the development and optimization of high-performance composite materials in civil engineering applications.

How do Ritz Vectors React to the Imposed Load?

All real structures behave dynamically when loaded or displaced. Additional inertial forces are equal to the force in acceleration using Newton's second law. If the forces or the change of places are applied very slowly, the inertial forces can be ignored and a static analysis can be done. Therefore, it can be said that dynamic analysis is a simple extension of static analysis. In addition, all potential real structures have unlimited degrees of freedom. Therefore, the most critical part of structural analysis is creating a model with a limited number of degrees of freedom that has several almost massless members and several nodes, which can estimate the behavior of the structure appropriately. The mass of the structure can be concentrated in the nodes. Also, for a linear elastic system, the stiffness characteristics of the members can be estimated very accurately - according to the experimental data - although the estimation of dynamic loading, energy loss, and boundary conditions can be very difficult. Therefore, the nonlinear dynamic analysis method is usually used in theoretical studies and is not used in routine designs. So, it is a worthwhile task to propose a simple and computer method for seismic estimation of structures. For this purpose, POA has been introduced. In many cases, we can get more valuable information from POA than nonlinear dynamic analysis, this method is simple and economical and has attracted more attention nowadays.

A FEM-based model for failure initiation in the microstructure of gray cast iron under uniaxial compression

PurposeThe purpose of this study was to validate the feasibility of the proposed microstructure-based model by comparing the simulation results with experimental data. The study also aimed to investigate the relationship between the orientation of graphite flakes and the failure behavior of the material under compressive loads as well as the effect of image size on the accuracy of stress–strain behavior predictions.Design/methodology/approachThis paper presents a microstructure-based model that utilizes the finite element method (FEM) combined with representative volume elements (RVE) to simulate the hardening and failure behavior of ferrite-pearlite matrix gray cast iron under uniaxial loading conditions. The material was first analyzed using optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) to identify the different phases and their characteristics. High-resolution SEM images of the undeformed material microstructure were then converted into finite element meshes using OOF2 software. The Johnson–Cook (J–C) model, along with a damage model, was employed in Abaqus FEA software to estimate the elastic and elastoplastic behavior under assumed plane stress conditions.FindingsThe findings indicate that crack initiation and propagation in gray cast iron begin at the interface between graphite particles and the pearlitic matrix, with microcrack networks extending into the metal matrix, eventually coalescing to cause material failure. The ferritic phase within the material contributes some ductility, thereby delaying crack initiation.Originality/valueThis study introduces a novel approach by integrating microstructural analysis with FEM and RVE techniques to accurately model the hardening and failure behavior of gray cast iron under uniaxial loading. The incorporation of high-resolution SEM images into finite element meshes, combined with the J–C model and damage assessment in Abaqus, provides a comprehensive method for predicting material performance. This approach enhances the understanding of the microstructural influences on crack initiation and propagation, offering valuable insights for improving the design and durability of gray cast iron components.

Generalized Effective Stress of Dual-Porosity Geomaterials Considering Thermochemical Effects

The accurate calculating of effective stress is crucial to predicting soil deformation and ensuring structural safety under complex mechanical, thermal, and chemical loads. In this study, the thermodynamic pressures of the solid phase, and liquid phases in macropores and micropores of dual-porosity geomaterials are determined on the basis of thermodynamics and conservation equations with considering for the impact of temperature and solute concentration on soil-water interactions. In particular, thermal pressurization related to temperature, and generalized osmotic pressure related to solute concentration were incorporated into the liquid-phase thermodynamic pressure equations. Thereafter, an equation for the generalized effective stress that could be applied specifically to dual-porosity geotechnical materials with consideration for environmental loads was derived from the definition of the stress tensor. The deformation behavior of clay under mechanical, thermal, and chemical coupling loading conditions was predicted using the newly proposed generalized effective stress. Predicted results revealed a stronger correlation between the generalized effective stress and void ratio, thereby confirming the accuracy and effectiveness of the proposed approach. The derived equation establishes a solid theoretical foundation for designing impermeable buffer barriers in geotechnical engineering and geo-environmental engineering safety assessments.

Effect of low velocity impact at different temperatures on hybrid adhesives in aluminium-composite single lap joints

This study aims to investigate the effect of a small stone impact on aluminum composite adhesive joints used in aircraft after exposure to various temperature conditions. In this context, single lap adhesive joints were prepared using 2024-T3 aluminium alloy sheets and 8-layer carbon fiber-reinforced epoxy hybrid composite sheets, with epoxy adhesive applied to the bonding surfaces. In addition, different types of hybrid adhesives were developed by reinforcing pure epoxy adhesive with various ratios (1%, 3% and 5% by weight) of graphene doped and undoped Nylon 6.6 (N6.6) nanofibers produced by electrospinning method to reduce brittleness. Low-velocity impact tests of 1.04 m/s under five different temperatures (−50, −20, 0, 23 and 50°C) were applied to all single lap adhesion joints produced and tensile tests were applied to the non-failed specimens to examine the loading conditions after low-speed impact. It was determined that approximately 1.5 J of the 3 J energy given by the low- velocity impact was absorbed in common in all samples, while the remaining part was returned and some separation occurred within the adhesion area due to the effect of this impact. While the low- velocity post-impact tensile strength of pure epoxy resin was measured as 2230.3 N at 23°C and 585.15 N at −50°C, the highest values were obtained in N6.6 reinforced epoxy adhesive with 1%GNP additive, which was measured as 3206.39 N at 23°C and 641.82 N at −50°C, and increased by 43.7% and 9.6% for 23°C and −50°C, respectively. In addition, the rupture surfaces of the specimens destroyed by the tensile test were examined by scanning electron microscopy (SEM) for damage analysis.

Investigation on the mechanical uncertainty of resistance spot weldings and its effect on structure crashworthiness of automotive B-pillars under side impacts

Resistance spot welding (RSW) is the main connection method for the white body structure of automobiles. Understanding the mechanical uncertainty of RSWs and its effect on structure crashworthiness design is of great significance for vehicle safety and lightweight design. In this work, the mechanical uncertainty of RSW was experimentally investigated and its effect on automotive B-pillar crashworthiness under side impacts was numerically analyzed based on a hybrid response surface model (HRSM). Firstly, the mechanical uncertainty of RSWs and associated failure mechanism were investigated and the fluctuation range of RSW strength under different loading conditions were quantified according to experimental results. Then, a reasonable RSW modeling method and subsystem collision simulation approach were demonstrated and the univariate sensitivity analysis was carried out to reveal the effect of RSWs’ mechanical property on B-pillar crashworthiness. Finally, a HRSM integrating Kriging polynomial and deep neural network (DNN) were proposed as surrogate model, based on which the multi-factor analysis was conducted to explore effects of RSW strength uncertainty on structure crashworthiness design.