Loss Of Cross-sectional Area Research Articles

Effect of test related factors on the degradation of cement-based materials on acetic acid exposure

Abstract Exposure of concrete to various acids can hardly be overstated due to the widespread use of concrete in the construction industry. The effect of selected factors on the degradation of ordinary Portland cement (OPC 53 grade) paste and mortar exposed to acetic acid is investigated in this paper. Various test parameters such as mass loss, loss in cross-sectional area, relative dynamic elastic modulus (RDEM), loss in flexural and compressive strength are used to assess the selected factors and the results obtained are analysed to determine the most favourable test conditions for degradation, that can be adopted for developing an accelerated test method. The factors used for the investigation are replenishment of acid solution, concentration of acid solution, ratio of surface area of specimen to volume of liquid acid solution (S/L), shape of the specimen and nature of the specimen. This paper also investigates the interrelationships among test parameters and adopts interpretation of acid consumption to assess the aggressiveness of the acid solution. It was found that renewing conditions and high concentrations of acid solution (0.5 M) indicate rapid degradation. The aggressiveness of 0.125 M acetic acid solutions in renewing conditions is about 5 times that of non-renewing conditions respectively. The rate of degradation is inversely related to S/L ratio. Cylindrical specimens have a marginal increase in degradation than prismatic specimens. It is preferable to evaluate acid attack on mortar specimens rather than paste specimens due to higher loss in cross-sectional area and relative dynamic elastic modulus (RDEM).

Ultrasound-derived rates of muscle wasting in the intensive care unit and in the post-intensive care ward for patients with critical illness: Post hoc analysis of an international, multicentre randomised controlled trial of early rehabilitation

Background and aimsMuscle wasting results in weakness for patients with critical illness. We aim to explore ultrasound-derived rates of change in skeletal muscle in the intensive care unit (ICU) and following discharge to the post-ICU ward. DesignPost hoc analysis of a multicentre randomised controlled trial of functional–electrical stimulated cycling, recumbent cycling, and usual care delivered in intensive care. MethodParticipants underwent ultrasound assessment of rectus femoris at ICU admission, weekly in the ICU, upon awakening, ICU discharge, and hospital discharge. The primary outcome was rate of change in rectus femoris cross-sectional area (ΔRFCSA) in mm2/day in the ICU (enrolment to ICU discharge) and in the post-ICU ward (ICU discharge to hospital discharge). Secondary outcomes included rate of change in echo intensity (ΔEI), standard deviation of echo intensity (ΔEISD), and the intervention effect on ultrasound measures. Echo intensity is a quantitative assessment of muscle quality. Elevated echo intensity may indicate fluid infiltration, adipose tissue, and reduced muscle quality. Results154 participants were included (mean age: 58 ± 15 years, 34% female). Rectus femoris cross-sectional area declined in the ICU (−4 mm2/day [95% confidence interval {CI}: −9 to 1]) and declined further in the ward (−9 mm2/day [95% CI: −14 to −3]) with a mean difference between ICU and ward of −5 mm2/day ([95% CI: −2, to 11]; p = 0.1396). There was a nonsignificant difference in ΔEI between in-ICU and the post-ICU ward of 1.2 ([95% CI: −0.1 to 2.6]; p = 0.0755), a statistically significant difference in ΔEISD between in-ICU and in the post-ICU ward of 1.0 ([95% CI, 0.5 to 1.5]; p = 0.0003), and no difference in rate of change in rectus femoris cross-sectional area between groups in intensive care (p = 0.411) or at hospital discharge (p = 0.1309). ConclusionsMuscle wasting occurs in critical illness throughout the hospital admission. The average rate of loss in muscle cross-sectional area does not slow after ICU discharge, even with active rehabilitation.

Reduced Fascicle Area Demonstrated in Ilioinguinal Nerves Resected from Primary Inguinal Herniorrhaphy Patients as Evidence of Compression Neuropathy.

30 male patients with primary inguinal hernias undergoing primary inguinal herniorrhaphy were prospectively recruited for ilioinguinal nerve resection and evaluation. Three samples of the resected ilioinguinal nerve (proximal, canal, and distal) were evaluated using Masson's trichrome stain to measure fascicle and total nerve cross-sectional area and detect changes in collagen. The fascicle cross-sectional area in the canal segment was significantly decreased compared to the proximal control with a large effect size observed (p = 0.016, η2 = 0.16). There was no significant difference in the nerve cross-sectional area between locations, but there was a moderate to large effect size observed between locations (p = 0.165, η2 = 0.105). There was no significant difference in collagen content nor effect size observed between locations (p = 0.99, η2 = 1.503 × 10-4). Interpretation. The decrease in the fascicle cross-sectional area within the inguinal canal further suggests that there is chronic pressure applied by hernia tissue consistent with axon degeneration. Collagen content is uniformly distributed along the length of the nerve. Further studies with larger samples are needed to confirm the observed effect of nerve location on the total nerve cross-sectional area and axon loss.

Protective role of pretreatment with Anisodamine against sepsis-induced diaphragm atrophy via inhibiting JAK2/STAT3 pathway

There is an increasing tendency for sepsis patients to suffer from diaphragm atrophy as well as mortality. Therefore, reducing diaphragm atrophy could benefit sepsis patients' prognoses. Studies have shown that Anisodamine (Anis) can exert antioxidant effects when blows occur. However, the role of Anisodamine in diaphragm atrophy in sepsis patients has not been reported. Therefore, this study investigated the antioxidant effect of Anisodamine in sepsis-induced diaphragm atrophy and its mechanism. We used cecal ligation aspiration (CLP) to establish a mouse septic mode and stimulated the C2C12 myotube model with lipopolysaccharide (LPS). After treatment with Anisodamine, we measured the mice's bodyweight, diaphragm weight, fiber cross-sectional area and the diameter of C2C12 myotubes. The malondialdehyde (MDA) levels in the diaphragm were detected using the oxidative stress kit. The expression of MuRF1, Atrogin1 and JAK2/STAT3 signaling pathway components in the diaphragm and C2C12 myotubes was measured by RT-qPCR and Western blot. The mean fluorescence intensity of ROS in C2C12 myotubes was measured by flow cytometry. Meanwhile, we also measured the levels of Drp1 and Cytochrome C (Cyt-C) in vivo and in vitro by Western blot. Our study revealed that Anisodamine alleviated the reduction in diaphragmatic mass and the loss of diaphragmatic fiber cross-sectional area and attenuated the atrophy of the C2C12 myotubes by inhibiting the expression of E3 ubiquitin ligases. In addition, we observed that Anisodamine inhibited the JAK2/STAT3 signaling pathway and protects mitochondrial function. In conclusion, Anisodamine alleviates sepsis-induced diaphragm atrophy, and the mechanism may be related to inhibiting the JAK2/STAT3 signaling pathway.

Vitamin D as an intervention for improving quadriceps muscle strength in patients after anterior cruciate ligament reconstruction: study protocol for a randomized double-blinded, placebo-controlled clinical trial

BackgroundThe goal of anterior cruciate ligament reconstruction (ACLR) is to restore the preinjury level of knee function to return to play (RTP). However, even after completing the rehabilitation programme, some patients may have persistent quadriceps muscle weakness affecting knee function which ultimately leads to a failure in returning to play. Vitamin D has been long recognized for its musculoskeletal effects. Vitamin D deficiency may impair muscle strength recovery after ACLR. Correcting vitamin D levels may improve muscle strength.MethodsThis is a double-blinded, randomized controlled trial to investigate the effects of vitamin D supplementation during the post-operative period on quadriceps muscle strength in anterior cruciate ligament (ACL)-injured patients. Patients aged 18–50 with serum vitamin D < 20 ng/ml, unilateral ACL injury, > 90% deficit in total quadriceps muscle volume on the involved leg compared with uninvolved leg, Tegner score 7 + , and no previous knee injury/surgery will be recruited. To assess patient improvement, we will perform isokinetic and isometric muscle assessments, ultrasound imaging for quadriceps thickness, self-reported outcomes, KT-1000 for knee laxity, biomechanical analysis, and Xtreme CT for bone mineral density. To investigate the effect of vitamin D status on quadriceps strength, blood serum samples will be taken before and after intervention.DiscussionPatients with low vitamin D levels had greater quadriceps fibre cross-sectional area loss and impaired muscle strength recovery after ACL. The proposed study will provide scientific support for using vitamin D supplementation to improve quadriceps strength recovery after ACLR.Trial registrationClinicalTrials.gov NCT05174611. Registered on 28 November 2021.

Local–overall buckling behavior of corroded intermediate compression-bending H-section steel columns

The primary aim of this paper is to assess the impact of corrosion damage on intermediate H-section steel columns subjected to combined compression and bending about the strong axis. The study conducted a comprehensive investigation into the corrosion-induced transition in the buckling behavior of steel columns through experimental and numerical analyses. Six H-section Q355 steel intermediate columns were designed, with five undergoing an artificial spray-accelerated corrosion process. The three-dimensional scanning technology was employed to quantify the general corrosion and corrosion pits. Eccentric compression tests were carried out on intermediate H-section steel columns to investigate the effect of the different corrosion levels on the failure mode and load-displacement curves, as well as to determine local buckling load based on the load-strain curves. The test results showed that the corrosion characteristic parameters of each cross-section of the steel column exhibited irregularity and variation in all locations, reflecting the heterogeneity of corrosion. The density of corrosion pits exhibited a decreasing trend with increased corrosion duration. Corrosion remarkably reduced both the ultimate carrying capacity and local buckling capacity, with the most severely corroded specimen exhibiting an average cross-sectional area loss rate of 37 %, resulting in a 43 % and 51 % reduction in ultimate load and buckling load compared to the uncorroded specimen. Furthermore, the corrosion features substantially influenced the failure mode, resulting in a transition from overall buckling to local buckling or local-global interaction buckling. A numerical methodology was developed to incorporate the actual surface morphology of corrosion, and the reliability of the modeling method was validated through comparison with experimental results, further revealing the failure mechanism of corroded intermediate H-section steel columns under compression and bending about the strong axis.

Experimental investigation of the efficiency of stone revetment for different temporal variations with the static water condition

Abstract The objective of this study is to determine the optimum size of stone revetment for different water standing durations and critical drawdown rates for 80% height of flood. The model bank was constructed using soil sourced from the Parlalpur ferry ghat of the Ganga River in Kaliachak, West Bengal, with a field density of 1.5 g/cc achieved by maintaining a 10% moisture content (MC) in the model bank soil. The model river bank was prepared considering Froude (F) similitude having a distorted depth scale of 1/20 and a linear scale of 1/200. In this study, effective stone sizes (D10) – 2.3, 3.22, 4.58, 6.31, and 8.84 mm – were used. These stone sizes were investigated in conjunction with three water standing durations: 15, 30, and 45 min. The bank slope was prepared at 1V:1.5H, and a drawdown ratio of 80% was maintained. The effectiveness of stone revetment size was analysed in terms of the percentage loss of stone revetment and the percentage loss of the model bank's cross-sectional area. The outcomes of this study indicate that the 6.31 mm stone size exhibits optimal performance.

Prediction of Crack Width in RC Piles Exposed to Local Corrosion in Chloride Environment.

A novel prediction model for crack development of reinforced concrete (RC) piles with localized chloride corrosion in the marine environment is proposed. A discrete method is used to solve the corrosion pit radius model and a crack extension model is developed to investigate the initiation and extension of cracks. The maximum corrosion degree of the reinforced concrete pile is predicted according to the limit crack criterion, and finally, a sensitivity analysis is carried out on the important parameters of crack extension. The results show that the radius of the corrosion pit, the depth corrosion pit, and the cross-sectional area loss of reinforcement gradually increase as the corrosion level increases. The loss of the local reinforcement section at crack initiation increases with the increase in the ratio of concrete cover to initial diameter and increases with the increase in the pitting factor. The required pit depth for reinforcement cracking increases with the increase in the ratio of concrete cover thickness to diameter. The loss of the cross-sectional area of reinforcement and the radius of the corrosion pit increase with the increase in the initial diameter of reinforcement. Increasing the pitting factor can reduce the pit depth and make the crack width develop faster before reaching the limit crack width. Increasing the concrete cover thickness can provide an improvement in the propagation of cracks. A comparative analysis shows that the localized corrosion pattern is more in conformity with marine engineering practice.

Evaluation of residual flexural behavior of corroded fiber-reinforced super workable concrete beams

This study investigates the effect of macro synthetic fiber (MSF) volume and crack widths on corrosion of the reinforcing bars and residual flexural behavior of fiber-reinforced super-workable concrete (FR-SWC) beams exposed to accelerated corrosion. FR-SWC beams prepared with 0, 0.33%, and 0.66% MSF were pre-cracked at 0.2-, 0.4-, and 0.75-mm widths before corrosion testing. The controlled crack width was initiated in one set of beams that were then unloaded. The crack width was maintained for another set of beams during corrosion testing by inserting a shim. Test results showed that the use of 0.33% and 0.66% MSF reduced crack development and crack propagation, delayed corrosion initiation time, and significantly increased the residual flexural strength of beams subjected to accelerated corrosion. The beams reinforced with 0.66% MSF enhanced residual ultimate load, residual yield load, and residual flexural toughness by 10%–45%, 38%–113%, and 42%–150% compared to the corresponding non-fibrous beams. The improved flexural performance of beams made with MSF after accelerated corrosion can be attributed to the ability of MSF to reduce crack width due to corrosion damage. Crack width lower than 0.2 mm showed no significant effect on the residual flexural behavior of beams after corrosion testing. However, the pre-crack width over 0.2 mm showed a significant influence on the crack initiation and residual flexural behavior after accelerating corrosion. The pre-cracked beams with a 0.75 mm crack width retained the ultimate load of 65%–76%, yield load of 47%–80%, and toughness of 38%–83%, respectively, compared to their corresponding uncracked beams subjecting to accelerated corrosion. The un-shimmed beams allowed partial closure of cracks due to the presence of MSF after initial loading and increased the residual ultimate load, yield load, and flexural toughness by 7%–45%, 27%–82%, and 3%–56%, respectively, compared to their corresponding shimmed beams. A correlation between the residual flexural behavior and the rate of cross-sectional area loss of reinforcing bars due to corrosion was developed. Furthermore, a mechanism was proposed to explain the effect of MSF in improving the residual flexural performance in the cracked FR-SWC beams.

The importance of serial sarcomere addition for muscle function and the impact of aging.

During natural aging, skeletal muscle experiences impairments in mechanical performance due, in part, to changes in muscle architecture and size, notably with a loss of muscle cross-sectional area. Another important factor that has received less attention is the shortening of fascicle length, potentially reflective of a decrease in serial sarcomere number (SSN). Interventions that promote the growth of new serial sarcomeres, such as chronic stretching and eccentric-biased resistance training, have been suggested as potential ways to mitigate age-related impairments in muscle function. While current research suggests it is possible to stimulate serial sarcomerogenesis in muscle in old age, the magnitude of sarcomerogenesis may be less than in young muscle. This blunted effect may be partly due to age-related impairments in the pathways regulating mechanotransduction, muscle gene expression, and protein synthesis, as some have been implicated in SSN adaptation. The purpose of this review was to investigate the impact of aging on the ability for serial sarcomerogenesis, and elucidate the molecular pathways that may limit serial sarcomerogenesis in old age. Age-related changes in mTOR, IGF-1, myostatin, and serum response factor signalling, MuRFs, and satellite cells may hinder serial sarcomerogenesis. In addition, our current understanding of SSN in older humans is limited by assumptions based on ultrasound-derived fascicle length. Future research should explore the effects of age-related changes in the identified pathways on the ability to stimulate serial sarcomerogenesis, and better estimate SSN adaptations to gain a deeper understanding of the adaptability of muscle in old age.

Area-loss effect analysis of pin-jointed structures

Corrosion will cause cross-sectional area loss of steel members, which will lead to redistribution of internal force and affect the performance of structures. In this paper, a generalized formula for the internal force variation of pin-jointed structures due to variation of external force, cross-sectional area, and initial length is derived. The area-loss sensitivity coefficient ( ASC) and the area-loss evenness coefficient ( AEC) based on statistical measures are then defined. By calculating these two coefficients, the influence of single member’s area-loss on the behavior of the structure as well as the evenness of internal force variation are evaluated. Besides, a method to determine the area-loss limit of pin-jointed structures is proposed based on the structural reliability theory and mathematical nonlinear programming. According to the above process, the effect of members’ area loss on structural properties is analyzed without complicated numerical approaches such as FEM, and then the safety of corroded structures is assessed preliminarily. The proposed method is verified by two numerical examples, and provides a convenient tool for pre-manufacturing, maintenance during service life, and structural health monitoring of pin-jointed structures.

Life-Cycle Cost Assessment Using the Power Spectral Density Function in a Coastal Concrete Bridge

Recently, the repair and maintenance of structures has been necessary to prevent these structures’ sudden collapse and to prevent human and financial damage. A natural factor in marine environments that destroys structures and reduces their life is the presence of chloride ions. So regular health monitoring of concrete coastal buildings for on-time repair is essential. This study investigates the performance of the power spectral density (PSD) method as a non-destructive damage-detection method to monitor the location and amount of damage caused by chloride ions during a structure’s life using different approaches according to life-cycle assessment (LCA) and life-cycle cost assessment (LCCA). In this regard, chloride corrosion damage dependent on zone distance from seawater was first calculated to obtain the service life of each part of a coastal concrete bridge according to the conventional method. Based on rebar corrosion each year, the next stage forecasted the bridge’s concrete deterioration. The PSD method monitored the annual loss of reinforcement cross-sectional area, changes in dynamic characteristics such as stiffness and mass, and the bridge structure’s life using sensitivity equations and the linear-least-squares algorithm. Finally, according to the location and quality of damage in each year of bridge life until the end of life, LCC and maintenance and repair costs of the PSD method were compared with the conventional method. The results showed that this strategy was very effective at lowering and optimizing the costs of maintenance and repair caused by chloride corrosion.

ASSESSMENT OF THE STABILITY OF MINE HAULAGE DRIFT USING STATISTICAL ANALYSIS OF ARCH YIELDING SUPPORT FAILURE

Purpose. The stability of mine haulage drift has been evaluated using statistical analysis of arch yielding support failure under different protective measures to create safe working conditions for miners in deep coal mines with steeply dipping seams. Methods. A comprehensive approach was used, including a mine experiment , probability theory methods, and statistical analysis of experimental data. Results. The stability of mine haulage drift on steep seams was assessed in natural conditions under different protective measures. It was found that while using post-and-lintel support to protect the drift, with an arch yielding support failure frequency of w≥0.56 and normal distribution of single-factor dispersion analysis statistics, the loss of cross-sectional area of the excavation over the length of the mining site was about 50%. While using cribbing support for protection, with an arch yielding support failure frequency of w≥0.29, the loss of cross-sectional area was 30%. Empirical frequency w of the arch yielding support failure along the length of the excavation does not differ from theoretical frequencies, allowing the probability of an event related to deterioration of the stability of the mine haulage drift along the length of the mining site to be determined within a confidence interval under different protective measures. Novelty. A functional dependence was established to evaluate the stability of the mine haulage drift under different protective measures along the length of the mining site using single-factor dispersion analysis statistics of arch yielding support failure. Practical significance. Based on the statistical analysis of arch yielding support failure installed in the mine haulage drift, it is advisable to consider that the operational condition of the preparatory workings is ensured when using protective structures in the form of wooden cribbing support.

Axial compression behavior of stub square concrete-filled steel tubes with regional defect

This paper investigated the axial compression behavior of stub square concrete-filled steel tubes with simulated local corrosion damage through a series of tests. The local corrosion damage was simulated by machining a regional defect on the tube. Aiming at the test specimens, the noteworthy observations were recorded, the load-shortening curves were developed, and the influence of the defect dimensions on the compressive performance of the specimens was discussed. The results revealed that the local defect on the steel tube can lead to the loss of confinement on the core concrete and the centroid offset of the specimen. Therefore, the increase in the defect sizes decreased the ultimate resistance of the specimen. When the local defect sizes reached 150 mm (length) × 112.5 mm (width) × 3.5 mm (depth), the ultimate resistance and the ductility of the specimen decreased to 88.2 % and 65.8 % of the intact specimens, respectively. Furthermore, based on the experimental study and the theoretical analysis, with consideration of the cross-sectional area loss and the confinement loss, a method was proposed to predict the ultimate resistance of the specimens with the local defect, which also can be adopted to evaluate the residual resistance of the locally corroded members in service.

Ultrasonic guided wave testing on pipeline corrosion detection using torsional T(0,1) guided waves

Ultrasonic guided wave testing (UGWT) is used in rapid screening to detect, locate and classify corrosion defects. This non-destructive testing technique can perform wide-range inspection from a single point, thus reducing the time and effort required for NDT. However, the mode conversion phenomena and the dispersive nature of the guided waves make corrosion detection difficult. Hence, the parametric studies on the response signals of a T (0, 1) wave from pipe defects were presented in this paper. Firstly, a mathematical model of 6-inch schedule 40 pipes was developed. The corrosion profile of various geometries was then constructed on the outer surface of the pipeline by varying the circumferential length and depth. The numerical study was performed to analyse the characteristics of the response signals when a torsional guided wave impinges on the corroded pipelines. A five-cycle Hanning tone-burst signal with a central frequency of 30k Hz was used throughout the study. The results demonstrated that mode conversion to a flexural mode F (1, m) occurs when the stimulated T (0, 1) strikes non-symmetric defects. Nonetheless, as the circumferential extent of the corrosion increased, the response signals tended to behave symmetrically, and there was less mode conversion detected. Thus, the presence of flexural mode F (1, m) can be used as the criteria to distinguish symmetric and asymmetric faults. In addition, the results demonstrated that the reflection coefficients increase monotonically with the defect's depth due to the increases in the estimated cross-sectional area loss (ECL). As a result, a more significant proportion of the transmission wave was reflected. These findings serve as guidelines for on-site inspections. With the known speed of guided wave propagation, it is possible to precisely forecast the position of faults.

Designing and Investigating a Nondestructive Magnetic Flux Leakage Detection System for Quantitatively Identifying Wire Defects

In-haul cables must be examined and maintained regularly to ensure the smooth operation of cable-stayed bridges. The magnetic flux leakage (MFL) detection method is being applied increasingly commonly to inspect defects. For the quantitative identification of the broken wire, we designed an MFL inspection equipment and investigated the performance. A trapezoidal magnetic dipole model is constructed to simulate the leakage distribution, and the axial and circumferential excitation schemes are used to obtain the intensity of magnetic induction. Then, based on the simulation of model parameters, an MFL detection system is configured for detecting the damage in the broken wire. To investigate the adaptability of the developed system, a rectangular defect is inspected in the vertical and spiral climbing modes. The signal acquired under different paths is processed by the median filtering and wavelet transform methods and analyzed. A random forest algorithm is used to quantitatively identify the number of broken wires, defect dimensions, and cross-sectional area loss to verify the proposed method. The results show that the axial excitation generates a single peak signal, which offers better detection of the wire defects. In the vertical climbing mode, the maximum detection errors in the width and cross-sectional area loss are 0.64 mm and 0.46%, respectively, while the values are 0.21 mm and 0.1% in the spiral climbing mode, indicating that the latter mode offers higher identification accuracy. Furthermore, in future work, the detection capability of irregular defects should be studied, expanding its application in health monitoring.

Internal calibration for opportunistic computed tomography muscle density analysis.

Muscle weakness can lead to reduced physical function and quality of life. Computed tomography (CT) can be used to assess muscle health through measures of muscle cross-sectional area and density loss associated with fat infiltration. However, there are limited opportunities to measure muscle density in clinically acquired CT scans because a density calibration phantom, allowing for the conversion of CT Hounsfield units into density, is typically not included within the field-of-view. For bone density analysis, internal density calibration methods use regions of interest within the scan field-of-view to derive the relationship between Hounsfield units and bone density, but these methods have yet to be adapted for muscle density analysis. The objective of this study was to design and validate a CT internal calibration method for muscle density analysis. We CT scanned 10 bovine muscle samples using two scan protocols and five scan positions within the scanner bore. The scans were calibrated using internal calibration and a reference phantom. We tested combinations of internal calibration regions of interest (e.g., air, blood, bone, muscle, adipose). We found that the internal calibration method using two regions of interest, air and adipose or blood, yielded accurate muscle density values (< 1% error) when compared with the reference phantom. The muscle density values derived from the internal and reference phantom calibration methods were highly correlated (R2 > 0.99). The coefficient of variation for muscle density across two scan protocols and five scan positions was significantly lower for internal calibration (mean = 0.33%) than for Hounsfield units (mean = 6.52%). There was no difference between coefficient of variation for the internal calibration and reference phantom methods. We have developed an internal calibration method to produce accurate and reliable muscle density measures from opportunistic computed tomography images without the need for calibration phantoms.

Suggestion of Practical Application of Discrete Element Method for Long-Term Wear of Metallic Materials

This study presents a simulation procedure for the wear of metallic materials exposed to long-term cumulative contact forces and introduces a numerical analysis procedure using the discrete element method (DEM) to predict the wear damage. Since the DEM can calculate the motion and contact load of each particle and the interaction between particles for each dynamic collision of particles, it was possible to analyze the motion of the particles causing metal wear. A method to reflect particle size, material properties, and long-term cumulative friction distance required by the DEM was proposed so that the collision and friction load between particles can be predicted practically. Considering the feature of wear suggested by Archard, it was shown that the wear amount can be predicted efficiently by converting the long-term load into an equivalent material constant. In addition, it was suggested that it is reasonable to determine the size of the particles in consideration of the size of the surface mesh of the metal surface. The accuracy of the analysis results obtained using the procedure proposed in this study was compared with that of the wear test results of metal material specimens presented by former studies. The numerical analysis was also performed in the reference study, but inaccurate results were derived compared to the analysis results. The reason for the inaccuracy of the numerical model performed in the previous study was found to be environmental factors that cannot be considered in a numerical analysis. In this study, it was determined that it was because the behavior of particles and the load transferred to the specimen were not well simulated, which remains a problem for future research. As a result, it was confirmed that it is possible to compute a worn shape similar to the measured shape of experiments. Thereafter, the change in the contact load predicted by simulation is discussed in terms of wear shape and cross-sectional area loss ratio.

Degradation of artificially corroded galvanized high-strength steel wires: Corrosion morphology and mechanical behavior

• Four typical pit morphologies exist on the corroded steel wires. • Pit depth and uniform corrosion depth are in constant competition while the competition tends to stabilize when corrosion loss is more than 10%. • Ductility degradation is greater than strength and the ductility degradation is related to the ratio of pit depth to residual radius. The corrosion morphology of artificially galvanized high-strength steel wires and its effect on mechanical behavior was presented. The corrosion morphology was obtained by 3D optical scanner. Four typical pit morphologies on corroded wires were identified, namely conical pit, hemispherical pit, combined pit and secondary pit. The probabilistic density function of cross-sectional parameters under different corrosion degree were modeled by normal distribution, and the evolution of model parameters was obtained. Based on the proposed evolution model, the maximum cross-sectional area loss was estimated by ‘3 σ rule’ of normal distribution function. Subsequently, the effect of corrosion pits on the mechanical behavior of corroded wires was discussed. It shows that the ductility degradation of corroded wires is much greater than that of strength, the ductility degradation is closely related to the ratio of pit depth to residual radius. Besides, it was found that the probabilistic density function of the ratio of pit depth to uniform corrosion depth tends to stabilize when the corrosion loss is more than 10%, which indicates that the surface of corroded wire with corrosion pits is uniformly thinning.

Experimental study on mechanical properties and low-cycle fatigue behaviour of stainless steels subjected to salt spray and dry/wet cycle

This paper presents experimental studies on the mechanical properties and low-cycle fatigue behaviour of corroded austenitic stainless steel (304) and ferritic stainless steel (430). Tensile and low-cycle fatigue tests are conducted on 28 specimens. The corrosion process of the specimens is finished by using salt spray and dry/wet cycle tests. In the tensile tests, the key parameters of the constitutive model proposed by both Rasmussen and Gardner were obtained for austenitic stainless steel (304) and ferritic stainless steel (430). In the low-cycle fatigue test, the relationships of the stress amplitude and fatigue life of the specimens were obtained. The relationships of the mass loss, corrosion rate and cross-sectional area loss with the corrosion time are established. The influences of corrosion pits and fatigue cracks on the low-cycle fatigue behaviour of these two materials are studied through both macro and micro fracture morphology analysis. It is found that compared with the salt spray, the dry/wet cycle condition causes more degradation on the strength and fatigue life of the ferritic stainless steel (430). The stress concentration and notch effect of corrosion pits are the main reasons for the degradation in fatigue life of ferritic stainless steel (430). Moreover, current codes Eurocode 3 (EC3), Australian Standard (AS), BSI Standard (BSI) and DNV Standard (DNV) could not provide accurate fatigue life assessment for these two materials after salt spray and dry/wet cycle corrosions.