Impact Tests Research Articles

Studying the Hygrothermal Effects on the Impact Responses of Composite Materials Under Various Environmental Conditions

The current study focuses on the effects of different weather conditions, including temperature and humidity, on the impact energy properties of composite materials tested using a Charpy impact tester connected to a special hygro-thermal device. This is a unique device, handcrafted and equipped with sensors and control panels The composite materials, used in this study, combine polyester and reinforced with fiberglass in various shapes and loadings. Nanopowder materials including titanium oxide nanoparticles (TiO2) and aluminum oxide nanoparticles (Al2O3) were also added to the composite materials and their effects were assessed. The obtained results showed that all the different factors studied in this research have a positive effect on the impact test, except the nanomaterials in both cases (Al2O3 and TiO2 nanopowders) at 2 wt.% of the sample and at approximately 10 wt.%. Hence, at this percentage, there is not enough effect on the impact energy

Tensile and Impact Properties of Woven Glass Fibers/Epoxy Composites Filled with Short Glass Fibers

Glass fiber/polymer composites are widely utilized in many structural applications because of their high specific strength and stiffness-to-weight ratios. In this study, woven glass fiber/epoxy was hybridized with short glass fibers of different lengths (2, 4, 6, 2+4, 2+6, and 4+6 mm) and contents (3, 6, 9, and 12 wt%) to produce hybrid woven SGF/epoxy composites. Variations in the thickness, fiber volume fraction, density, and void content of the prepared composites were determined. Mechanical tests such as tensile and Charpy impact tests were conducted. Compared to the woven fabric composites without short glass fibers (control samples), the tensile strength increased by approximately 13% at an optimum weight fraction of 3 wt% using short glass fiber lengths of 4 mm. Meanwhile, the incorporation of short glass fibers into the woven glass composites decreased the tensile modulus for all lengths. The maximum enhancement in the impact strength (approximately 14%) was achieved by the hybrid composite samples reinforced with 4 mm of short glass fibers at 3 wt%. This hybrid composite offers 18% and 20% improvements in the specific tensile and impact strengths, respectively. In summary, filling the woven fabric composites with specified short fiber contents and lengths can increase their mechanical performance when resin-rich regions are reinforced with short fibers without forming relatively thick interleaves between the woven fabric plies

Analysis of the structural integrity of wooden structures in service: case study with diagnostic methodologies and rehabilitation strategies

The rehabilitation, restoration, or reinforcement of wooden structures requires a thorough assessment of their "health" status. This evaluation is akin to Structural Integrity Assessment (SIA), which employs multidisciplinary techniques to determine the state of accumulated damage and its growth rate, enabling the prediction of the remaining service life of the structure and the scheduling of corrective actions. This case study aims to investigate the structural health of a wooden pergola in Belo Horizonte, MG, Brazil, applying SIA based on methods of propedeutics, diagnosis, and therapy. Non-destructive tests such as acoustic tomography, controlled penetration test (Resistograph), and impact test (Pilodyn) were conducted for propedeutics and diagnosis. Macroscopic visual assessment identified the wood species used in the pergola: Cumaru, Angelim Vermelho, and an unidentified species. The wood strength class was determined by the resistograph, and biotic, abiotic, and structural damages were evaluated. The structural performance analysis, considering the actual sections and the physical and mechanical characteristics of the wood, was performed using SAP 2000 software, with the verification of structural elements and connections according to the Brazilian standard NBR 7190. The study concludes by presenting therapies of a constructive nature, treatment and protection, and structural character.

Investigation on the effects of deposition strategy on the mechanical characteristics and microstructure of austenitic stainless steel 308LSi manufactured via wire arc additive manufacturing

This study examines the impact of deposition strategy on ASS 308LSi thin-walled structure manufactured via the Wire Arc Additive Manufacturing (WAAM) technique on the microstructural characteristics, tensile strength, microhardness, Charpy impact testing, and fracture morphology of the WAAM 308LSi. The analysis of the microstructure reveals that the deposition strategy promotes transitioning from columnar to equiaxed fine grain structure. The tensile strength results show that specimens with a 45° deposition strategy exhibit lower anisotropy and higher tensile properties compared to those with a 0° deposition strategy, with improvements of 33.1% in the transverse direction and 26.7% in the longitudinal deposition directions, respectively. The microhardness in WAAM SS308LSi demonstrates variations in the bottom, middle, and top regions, with the highest average value observed at a 45° deposition strategy (213.3 ± 6.5 HV, 201.1 ± 10.7 HV, and 191.5 ± 5.2 HV) as well. The impact testing results indicate that the highest absorbed energy occurs at a 45° deposition strategy, with 75 ± 4.2 J and 74 ± 4.0 J for the transverse and longitudinal directions, respectively. The fractures observed during testing exhibit ductile characteristics, with the presence of dimples and particles. This study demonstrates the significant potential of the 45° deposition strategy with the implementation of double-sided substrate deposition, resulting in a refined microstructure, nearly isotropic behavior, and excellent mechanical performance.

Impact of an Electronic Health Record-Based Interruptive Alert Among Patients With Headaches Seen in Primary Care: Cluster Randomized Controlled Trial.

Headaches, including migraines, are one of the most common causes of disability and account for nearly 20%-30% of referrals from primary care to neurology. In primary care, electronic health record-based alerts offer a mechanism to influence health care provider behaviors, manage neurology referrals, and optimize headache care. This project aimed to evaluate the impact of an electronic alert implemented in primary care on patients' overall headache management. We conducted a stratified cluster-randomized study across 38 primary care clinic sites between December 2021 to December 2022 at a large integrated health care delivery system in the United States. Clinics were stratified into 6 blocks based on region and patient-to-health care provider ratios and then 1:1 randomized within each block into either the control or intervention. Health care providers practicing at intervention clinics received an interruptive alert in the electronic health record. The primary end point was a change in headache burden, measured using the Headache Impact Test 6 scale, from baseline to 6 months. Secondary outcomes included changes in headache frequency and intensity, access to care, and resource use. We analyzed the difference-in-differences between the arms at follow-up at the individual patient level. We enrolled 203 adult patients with a confirmed headache diagnosis. At baseline, the average Headache Impact Test 6 scores in each arm were not significantly different (intervention: mean 63, SD 6.9; control: mean 61.8, SD 6.6; P=.21). We observed a significant reduction in the headache burden only in the intervention arm at follow-up (3.5 points; P=.009). The reduction in the headache burden was not statistically different between groups (difference-in-differences estimate -1.89, 95% CI -5 to 1.31; P=.25). Similarly, secondary outcomes were not significantly different between groups. Only 11.32% (303/2677) of alerts were acted upon. The use of an interruptive electronic alert did not significantly improve headache outcomes. Low use of alerts by health care providers prompts future alterations of the alert and exploration of alternative approaches.

Low-velocity impact behavior of foam-based sandwich composite reinforced with warp-knitted spacer fabric; numerical and experimental study

The aim of this research is to investigate experimentally and numerically the low-velocity impact behavior of foam-based composites reinforced with warp-knitted spacer fabric (WKSF). To prepare different foam-based composites, the structural parameters of WKSFs including cell size, position, and Z-fiber height were considered. A drop weight impact test with an initial energy of 5J was carried out to examine the low-velocity impact behavior of composites, followed by experimental analyses of Mises, shear, and normal stress on various composite components. Thereafter, the impact behavior of the composites was simulated using ABAQUS/CAE software. The comparison between experimental and numerical results showed a maximum error of 9.79% in predicting the acceleration of impactor. In addition, the results revealed significant stress disparities among samples. Stress analysis showed complex patterns across samples, emphasizing structural parameter influence on stress tolerance and load-bearing capabilities. Notably, Z-fibers displayed substantial stress tolerance, while the matrix predominantly undergoes shear stress. Consequently, the ideal structure for low-velocity impact applications includes small cell size, high thickness, and non-facing hexagonal cells.

Evaluation of the mechanical properties of hybrid composites reinforced with plant fibers

The incorporation of plant fibers into the matrix plays an interesting role. Natural fibers have been widely used as reinforcements in polymer matrix composites. Among all reinforcing fibers, natural fiber-based hybrid composites have attracted the attention of researchers as high-potential reinforcing materials for composite materials. These fibers are easily available in the form of agricultural products. Natural fibers are inexpensive, durable and lightweight materials for composite applications. In this experimental work, sisal fibers and date palm fibers were used as reinforcement in different ratios to fabricate hybrid composites by compression molding technique while maintaining a total fiber loading of 20 % by weight. Tensile tests, flexural tests, and impact tests were carried out, water absorption was also determined. The results obtained show that the composite composed of a combination of 16% sisal fibers and 8% date palm fibers has better tensile properties with a stress value of 6.88 N/mm2 and a value of Izod impact of 43.218 J/m. As well as both composites showed a better bending stress value of 67.29 N/mm2, the water absorption test was carried out for four days with 120 hours analysis. This research focuses on the fact that specimen-2 containing 16% sisal and 8% date palm fibers absorbs less water than other composites.

Thermal–Electrical–Mechanical Coupled Finite Element Models for Battery Electric Vehicle

The safety of lithium-ion batteries is critical to the safety of battery electric vehicles (BEVs). The purpose of this work is to develop a method to predict battery thermal runaway in full electric vehicle crash simulation. The thermal–electrical–mechanical-coupled finite element analysis is used to model an individual lithium-ion battery cell, a battery module, a battery pack, and a battery electric vehicle with 24 battery modules in a live circuit connection. The lithium-ion battery is modeled using a representative approach, with each internal battery component individually modeled to represent its geometric shape and realistic thermal, mechanical, and electrical properties. A resistance heating solver and Randles circuit model built with a generalized voltage source are used to simulate the electrical behavior of the battery. The thermal simulation of the battery considers the heat capacity and thermal conductivity of different cell components, as well as heat conduction, radiation, and convection at their interfaces. The mechanical property of battery cell and battery module models is validated using spherical punch tests. The electrical property of the battery cell and battery module models is verified against CircuitLab simulation in an external short-circuit test. The simulation results for the battery module’s internal resistance are consistent with both experimental data and literature values. The multi-physics coupling phenomenon is demonstrated with a cylindrical compression simulation on the battery module. The multi-physics BEV model with 24 live battery modules is used to simulate the external short-circuit test and the side pole impact test. The simulation run time is less than 24 h. The results demonstrated the feasibility of using a representative battery model and multi-physics analysis to predict battery thermal runaway in full electric vehicle crash analysis.

Dynamic mechanical properties of sandstone with two circular inclusions under impact loading

Inclusions are often present in rock defects, which can compensate for some of the problems of low rock strength and poor stability caused by hole defects. Specimens containing inclusions exhibit different mechanical properties under dynamic loading, and the strength change, energy evolution law and fracture mechanism deserve to be clearly discussed. In this work, a dynamic impact test of sandstone with circular inclusions was carried out. The failure process of each sample was recorded by a high-speed camera, and the influences of the inclusion strength and strain rate on the dynamic impact performance of the sandstone were analysed. Increasing the strain rate and inclusion strength can significantly improve the dynamic compressive strength of a sample. The dissipated energy density and impact toughness index are positively correlated with the strain rate. The dissipated energy density increased the most when the sample type was FA, at 10.6%. When the sample type was FD, the impact toughness index increased the most, which was 49.1%. In the early stage of loading, the localized strain is mainly concentrated inside the filler and gradually evolves into deformation of the filler and extension of shear cracks in the late stage of loading. The failure modes of a sample are not the result of a single factor but are influenced by both the strain rate and the filler. The types of cracks in the samples are mainly shear cracks and shear–tension composite cracks.

Dynamic behaviors of bridge with corroded RC piers under barge collisions

Reinforced concrete (RC) bridge piers located in navigable waterways are susceptible to chloride-induced corrosion, which may cause severe damage or even entire collapse of bridge under potential barge collisions. The present study aims to examine the failure patterns and dynamic responses of typical simply supported girder bridge with corroded RC piers under barge collisions. Firstly, nine RC column specimens with three designed corrosion degrees and two corrosion strategies were prepared using the impressed anodic current technique. Secondly, the drop hammer impact and axial compression tests were successively performed to examine the residual axial load bearing capacities of both unimpacted and impacted specimens. Furthermore, by comprehensively considering the effects of corrosion-induced deteriorations on the effective cross-sectional area and yield strength of reinforcements, concrete strength, as well as the rebar-concrete bond-slip relationship, the refined finite element (FE) models of specimens were established and validated. Finally, the dynamic behaviors of a prototype simply supported girder bridge with corroded RC piers under barge collisions at different service lives, i.e., 0–60 years, were numerically assessed. It indicates that: (i) under drop hammer impact, six specimens all exhibit global flexure failure, and relatively severe concrete cracking and spalling occur in the specimens with 15 % designed corrosion degree; (ii) the axial load bearing capacities of specimens with 5 % and 15 % designed corrosion degrees are reduced by 15.46 % and 34.86 % compared to the unimpacted non-corroded specimen, and 11.29 % and 43.30 % compared to the impacted non-corroded specimen; (iii) the transverse impact resulted in 25.93 %, 22.27 % and 35.53 % reductions in axial load bearing capacities for 0 %, 5 % and 15 % designed corrosion degree, respectively; (iv) for the prototype barge-bridge collision scenario, the failure patterns vary from minor bending cracks to remarkable flexural failure as the service live increases from 0 to 60 years. The corrosion-induced degradations of bridge performance should be concerned for the vessel collision-resistant design of bridge.

A review of Patient Reported Outcome Measures (PROMs) for characterizing Long COVID (LC)-merits, gaps, and recommendations.

Individuals may experience a range of symptoms after the clearance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. This condition is termed long COVID (LC) or Post-COVID-19 condition (PCC). Despite the appreciable number of symptoms documented to date, one key challenge remains in the robust characterization of LC outcomes. This review aimed to assess the properties, identify gaps, and provide recommendations for relevant descriptive and evaluative Patient-Reported Outcome Measurement (PROM) instruments that can be used to comprehensively characterize LC. To achieve this objective, we identified and reviewed descriptive and evaluative PROM instruments that have been developed and validated to date with people living with LC. Our review assessed their properties, identified gaps, and recommended PROMs suitable for characterizing LC. To ensure a comprehensive and robust characterization of LC, we next identified, reviewed, and selected (with the input of patient partners) PROMs associated with the most frequently reported LC symptoms. The evaluation criteria included psychometric evidence, mode of delivery, cost, and administration time. Traditional matrix mapping revealed Post-COVID Functional Status Scale (PCFS) as a choice instrument for capturing LC outcomes largely because of the comprehensive domains it covered, and the number of psychometric evidence reported in literatures. This instrument can be effectively paired with the Fatigue Severity Scale (FSS), Montreal Cognitive Assessment (MoCA), Patient Health Questionnaire (PHQ-9), Headache Impact Test (HIT), Pittsburgh Sleep Quality Index (PSQI), and DePaul Symptom Questionnaire (DSQ-PEM) to characterize fatigue, cognitive impairment, depression/anxiety, headache, sleeplessness, and post-exertional malaise respectively. Our paper identified appropriate PROM instruments that can effectively capture the diverse impacts of LC. By utilizing these validated instruments, we can better understand and manage LC.

Impact of annealing on the characteristics of 3D-printed graphene-reinforced PLA composite

Manufacturing through additive techniques, especially utilizing the fused filament fabrication (FFF) method, is a transformative technology revolutionizing design and manufacturing. FFF builds parts layer by layer using thermoplastic polymer and polymer composite filaments. However, weak interlayer connections often lead to low interlaminar resistance in printed structures. Recent studies suggest that post-deposition heat treatments can mitigate this issue by reducing internal thermal stresses and enhancing layer adhesion, thereby improving part properties. This research delves into the impact of annealing heat treatment on a composite of Polylactic Acid (PLA) reinforced with graphene. The annealing process was conducted at temperatures of 90, 100, and 120 °C for durations of 60, 120, and 240 min. The annealing response of the graphene-reinforced PLA composite is compared to that of natural PLA for reference, analyzing its effects on electrical, thermal, chemical, and mechanical properties. Chemical characterization was performed using X-ray diffraction (XRD), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). Thermal properties were analyzed via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Electrical properties were assessed by measuring resistance, resistivity, and conductivity. Mechanical properties were evaluated through tensile, flexural, notch sensitivity, impact tests, and hardness measurements. The results demonstrated that annealing of graphene-reinforced PLA and natural PLA did not alter their functional groups but increased their crystallinity. This treatment improved thermal stability, electrical conductivity, and mechanical properties, including tensile strength, flexural strength, and Shore D hardness. However, it reduced impact and notch sensitivity resistances. The increased crystallinity had a greater beneficial impact on some properties than the graphene reinforcement. These findings have potential applications in the automotive, aerospace, electronics, and medical sectors, given the increasing use of PLA in these industries.

Comparison of post-impact residual strength ratio between hybrid filament-wound cylinder and hybrid plate specimen

The filament-wound (FW) cylinders possess numerous benefits as a high-pressure storage device but are susceptible to impact loads. The presence of post-impact residual strength in an operating FW cylinder has the potential to accelerate the onset of failure. Ensuring the structural integrity and safety of the equipment requires thorough impact testing, which can be expensive and time-consuming, resulting in limited use. This article presents an innovative and cost-effective approach for conducting low-velocity impact testing on a hybrid Al/CFRP filament-wound cylinder by utilizing a simple hybrid Al/CFRP plate specimen. The main focus is to conduct low-velocity impact testing on both types of specimens, followed by post-damage testing that includes tensile tests on the hybrid plate specimen and burst tests on the FW cylinder. The results of laboratory experiments were compared to explicit and implicit numerical models conducted in a broad spectrum of impact energy range and found to be consistent. Using a parameter known as the post-impact residual strength ratio, it is possible to determine the expected impact loading conditions on the hybrid plate specimen that are equivalent to those experienced by the FW-cylinder. This low-cost impact testing method offers a practical and feasible solution to ensure the dependability and safety of FW cylinders throughout their operational lifespan.

Optimizing mechanical behavior in polymer bio-composites reinforced with basalt, graphene, and PP-g-MA

This paper aims to investigate the mechanical properties of bio-composites reinforced with basalt natural fibers/nanographene in polypropylene by incorporating pp-g-ma compatibilizer. The study employs the Response Surface Method with the Behnken box approach to formulate a novel mathematical model for bio-composite behavior based on the parameters of basalt fiber weight percentage, nanographene weight percentage, and PP-g-MA weight percentage. Unlike previous studies, our work uniquely integrates basalt fibers and nanographene to enhance tensile, bending, and impact strengths, achieving a composite with optimal mechanical properties. The performance of the research samples was evaluated through tensile, bending, and impact tests, with the results substantiated using Field Emission Scanning Electron Microscopy images. The failure surface in these samples revealed that the central mechanism influencing the performance of the introduced bio-composite is the failure of the fibers and their separation, accompanied by the stretching of the fibers from the base material. Subsequently, multi-objective optimization was conducted with the aim of increasing tensile strength, bending strength, and impact strength while reducing the weight of the samples. A Pareto diagram is presented based on the design goals. The outcomes indicate that the bio-composite sample values in the most suitable state for three mechanical characteristics including, tensile, impact, and bending strength are equal to 28, 90, and 49 MPa, respectively. This innovative combination and optimization significantly improve performance metrics, demonstrated through extensive testing and multi-objective optimization, which reveals the bio-composite’s superior mechanical characteristics.

Impact response of steel plate-concrete composite slabs with kinked rebar connectors

The steel plate-concrete (SC) composite slabs usually undergo large deformation under impact loading. To prevent early failure of the connectors and further improve the energy dissipation capacity, a novel kinked rebar connector (KR connector) is proposed for SC slabs. Pendulum impact tests on six specimens and numerical simulation are carried out to reveal the dynamic response and failure modes of KR-SC slabs with varying connector bending angles, diameters, and layout spacing. The results show that the finite element model can well predict the dynamic response of the KR-SC slabs under impact. The KR-SC slab reaches the best energy dissipation capacity at a connector bending angle of 45°.

Observation and modeling of dynamic fracture behaviors of battery cell under impact loading using enhanced representative volume element concept

The burgeoning electric automobile industry has increased interest in battery safety. Battery cells experience significant mechanical stress during operation, including the impact of accidents and vibrations from driving. The potential for thermal runaway reactions in battery cells raises safety concerns. Although numerous researchers have defined the dynamic behavior of battery cells and proposed numerical models to describe it, few studies have focused on the high-strain rate mechanical impact phase correlated with the onset of fracture. In this study, we describe the dynamic behavior of pouch battery cells and propose a modeling method to study their mechanical failure under impact situations. Impact tests are conducted at various velocities and heights. To overcome numerical issues commonly encountered under rapid deformation scenarios, a new finite element model is developed based on the representative volume element model. The proposed approach efficiently simulates continuous crack propagation and brittleness behavior during impact by permitting the individual behavior of the cell components. Therefore, engineers can reliably design safer electric vehicle battery cells by measuring the properties of the cell components.

Investigation on the dynamic failure characteristics of concrete slab based on mesoscopic simulation and energy conversion analysis

In this study, Continuous Discontinuous Element Method (CDEM) was employed to analyze the failure of concrete slab under drop-hammer impact at the mesoscopic level. Initially, simulation models of the impact system were established, and concrete slab models, including three-dimensional random aggregates, were generated. Mesoscopic simulations of concrete failure were then conducted by considering different variables, such as impact energy, slab size and the number of hammerheads. Corresponding drop hammer tests were used to validate the simulation results. Furthermore, an energy conversion formula for the dynamic failure of concrete slabs was derived, and the energy conversion process within the impact system was analyzed. The study also revealed the dynamic failure mechanisms of concrete slabs under various impact conditions. The research demonstrates that the simulation results are generally consistent with the impact tests. CDEM effectively investigates the impact characteristic and the energy conversion process of concrete slab failure. Under varying impact energies, slab sizes and hammerhead numbers, distinct differences in the failure characteristics of concrete-slab structure were observed. Increased impact energy accelerates the failure of concrete slabs, whereas larger concrete slab sizes inhibit crack propagation. The number of impact heads determines the initial crack position and its propagation path within the concrete slab. Moreover, the energy conversion process of the impact system significantly influences the failure behavior of the concrete slab. The effect of slab size on the energy utilization rate is greater than those of hammerhead number and impact speed.

Mechanical properties and strain rate effect of graphene oxide grafted carbon fiber modified concrete under dynamic impact load

In order to improve the shortcomings of carbon fiber, such as smooth surface, poor bonding with concrete matrix and easy to pull out under dynamic impact load, graphene oxide is grafted onto the surface of carbon fiber by chemical bonds to prepare graphene oxide grafted carbon fiber (CF-GO). The dynamic impact test on CF-GO modified concrete (CF-GOMC) is carried out by the split hopkinson pressure bar (SHPB) test system, and the mechanical properties and strain rate effect of CF-GOMC under dynamic impact loads are studied. The modification mechanism of CF-GO is analyzed by microscopic tests. The results show that compared with carbon fiber, the surface roughness and surface area of CF-GO increase and CF-GO is more suitable for bonding with concrete matrix. CF-GO can improve the mechanical properties of concrete under dynamic impact load and enhance the strain rate effect of dynamic mechanical properties indicators by preventing crack, bridging, filling and promoting hydration. With the increase of CF-GO content, the dynamic mechanical properties and strain rate sensitivity of CF-GOMC increase first and then decrease. The optimal content of CF-GO is 0.3 %. The improvement effect of CF-GO on the dynamic mechanical properties and strain rate effect of concrete is better than that of carbon fiber. The graphene oxide on the surface of CF-GO makes the interface of CF-GO/concrete matrix compact by improving the mechanical bite force of fiber/concrete matrix and promoting the formation of hydration products on the surface of fiber. The addition of CF-GO does not change the composition of cement hydration products, but promotes the crystal growth of hydration products and optimizes the pore structure of concrete.

Impact resistance and energy absorption characteristics of nickel-based alloy ring at elevated temperatures

To evaluate the high-temperature containment capability of a turbine casing, the impact resistance of half-ring specimens and full circular casings made of GH4169 nickel-based alloy was investigated. Ballistic impact tests were first conducted on GH4169 half-ring specimens using blade-shaped projectiles of DZ125 material fired from a single-stage gas gun. Meanwhile, explicit finite element simulations of the half-ring impact tests were performed with LS-DYNA. Comparing experimental and simulation results validated the accuracy of the model and revealed the effects of impact angle and ambient temperature. Then the process of a turbine casing containing a blade at 500 °C was simulated using the validated FE model. The results showed that the impact angle and the ambient temperature significantly affect the impact resistance of GH4169 half-ring specimen. Furthermore, the interaction mechanism between the turbine blade and casing differs across the three stages of the containment process.

Failure of a high-pressure flash gas pipeline from coal coke gasification to the cleaning section due to hydrogen-induced cracking

ABSTRACT The high-pressure flash pipeline of coal coke gasification leaked within one week after the operation. Further macroscopic observation showed that cracks appeared in the base material area near the weld. The medium transported by the pipe was low-concentration acid gas. Visual inspection, tensile testing, impact testing, chemical composition analysis, metallographic analysis, energy dispersive spectroscopy, X-ray diffraction analysis, and electron backscattering diffraction analysis were used to reveal the sources of cracks in the pipeline. It was found that the cracks were intergranular and filled with corrosion products. The chemical composition of the corrosion products is rich in Cr, S, and O. After the crack was opened, fracture features of ‘rock candy’ were observed, exhibiting brittle fracture characteristics. The cracks were caused by hydrogen-induced cracking along the grain boundary. On this basis, suggestions and countermeasures were put forward for the failure of the high-pressure flash gas pipeline.