The complete chloroplast genome of Leonurus sibiricus Linnaeus (Labiatae, Leonurus Miller).

Leonurus sibiricus Linnaeus 1753, an annual or biennial herb found in northern China, Mongolia, and Russia, typically grows in stony, sandy grasslands, and pine forests. This study sequenced and reported the complete chloroplast genome of L. sibiricus for the first time. The entire circular genome measures 151,689 bp in length, with a GC content of 38.4%. A total of 133 genes were annotated, including 88 protein-coding genes, 37 tRNAs, and eight rRNAs. The genome exhibits a typical quadripartite structure, comprising a large single-copy (LSC 82,820 bp) region, a small single-copy (SSC 17,619 bp) region, and a pair of inverted repeat (IR 25,625 bp each) regions. Phylogenetic analysis using the maximum-likelihood method indicates that L. sibiricus is most closely related to L. japonicus Houttuyn. This study provides valuable genomic resources for further research on the phylogenetics and biodiversity of the genus Leonurus.

The complete chloroplast genome of Pulsatilla chinensis f. alba D. K. Zang (Ranunculaceae, Pulsatilla Miller).

Pulsatilla chinensis f. alba D. K. Zang 1993 is a forma of Pulsatilla chinensis (Bge.) Regel, the root of P. chinensis is traditional Chinese medicine called Pulsatillae radix. The biggest difference between P. chinensis f. alba and P. chinensis is that P. chinensis f. alba sepals is white. The complete chloroplast genome of P. chinensis f. alba was sequenced using the Illumina NovaSeq platform for the first time. The lengths of the genome, large single-copy (LSC), small single-copy (SSC), two inverted repeats (IRs), and GC content were 163,654 bp, 82,355 bp, 19,069 bp, 31,115 bp, and 37.2%, respectively. It had 134 genes, including 90 protein-coding genes, 36 tRNA genes, and eight rRNA genes. The maximum-likelihood tree indicated that P. chinensis f. alba had a closer relationship with P. chinensis. This study would provide a theoretical basis for the further study of Pulsatilla plants genetics phylogenetic research.

Selection, Identification, and Transcript Expression Analysis of Antioxidant Enzyme Genes in Neoseiulus barkeri after Short-Term Heat Stress.

Phytoseiid mite Neoseiulus barkeri is a crucial biological control agent utilized to control pest mites and many insects in crops all over the world. However, they are vulnerable to multiple environmental pressures, with high-temperature stress being the most significant challenge. Heat stress disrupts the balance of reactive oxygen species (ROS) levels in organisms, resulting in oxidative stress within the body. Antioxidant enzymes play a crucial role in effectively neutralizing and clearing ROS. In this study, comparative transcriptomics and quantitative real-time PCR (qRT-PCR) were employed to assess the impact of short-term heat stress on the transcript expression of antioxidant enzyme genes in N. barkeri. We primarily identified four antioxidant enzyme genes (NbSOD, NbPrx, NbCAT, and NbGPX) in N. barkeri after exposure to short-term heat stress. Then, new data on the expression patterns of these genes were generated. RNA sequencing and bioinformatics analysis revealed that NbSOD belongs to the Fe/Mn family of superoxide dismutase (SOD), which was identified as MnSOD. NbPrx was classified as a 1-Cys peroxiredoxin of the peroxidase family, whereas NbCAT was recognized as a classical catalase, and NbGPX was determined as cytoplasmic glutathione peroxidase-1 (GPX1). Transcriptional expression analysis of these four genes was conducted at different high temperatures: 36 °C, 38 °C, and 40 °C for 2, 4, and 6 h. The results also showed that all four genes exhibited significant up-regulation in response to short-term heat stress. Similarly, the highest expression levels for NbSOD, NbPrx, and NbCAT were observed at 40 °C for 4 h. However, NbGPX displayed its maximum expression value at 38 °C for 4 h. Overall, the obtained data suggest that short-term heat stress increases levels of ROS generated inside living organisms, which disrupts the oxidative balance and leads to alterations in the expression levels of antioxidant enzyme genes.

The complete chloroplast genome sequence of Syringa oblata Lindl. var. alba Hort. ex Rehd. 1763 (Oleaceae).

Syringa oblata var. alba is a shrub or a small tree from China with high ornamental, medicinal, and edible value. Here, we present its first complete chloroplast genome. The entire circular genome is 155,648 bp in length, with large single-copy (LSC) length of 86,247, small single-copy (SSC) length of 17,937, inverted repeat (IR) length of 25,732, and GC content of 37.9%. One hundred and thirty-two genes, including 88 protein-coding, 36 tRNA, and eight rRNA genes were predicted. A phylogenetic tree of 25 plant species was constructed based on the maximum-likelihood method, indicating that S. oblata var. alba, S. vulgaris, and S. oblata form a sister group. This study will provide valuable basic information for phylogeny, species identification, and varieties breeding of this species.

Associations between urinary iodine concentration and the prevalence of metabolic disorders: a cross-sectional study.

Background: Few studies have examined the role of iodine in extrathyroidal function. Recent research has shown an association between iodine and metabolic syndromes (MetS) in Chinese and Korean populations, but the link in the American participants remains unknown. Purpose: This study aimed to examine the relationship between iodine status and metabolic disorders, including components associated with metabolic syndrome, hypertension, hyperglycemia, central obesity, triglyceride abnormalities, and low HDL. Methods: The study included 11,545 adults aged ≥ 18 years from the US National Health and Nutrition Examination Survey (2007-2018). Participants were divided into four groups based on their iodine nutritional status(ug/L), as recommended by the World Health Organization: low UIC, < 100; normal UIC, 100-299; high UIC, 300-399; and very high, ≥ 400. The Odds ratio (OR) for MetS basing the UIC group was estimated using logistic regression models for our overall population and subgroups. Results: Iodine status was positively associated with the prevalence of MetS in US adults. The risk of MetS was significantly higher in those with high UIC than in those with normal UIC [OR: 1.25; 95% confidence intervals (CI),1.016-1.539; p = 0.035). The risk of MetS was lower in the low UIC group (OR,0.82; 95% CI: 0.708-0.946; p = 0.007). There was a significant nonlinear trend between UIC and the risk of MetS, diabetes, and obesity in overall participants. Participants with high UIC had significantly increased TG elevation (OR, 1.24; 95% CI: 1.002-1.533; P = 0.048) and participants with very high UIC had significantly decreased risk of diabetes (OR, 0.83; 95% CI: 0.731-0.945, p = 0.005). Moreover, subgroup analysis revealed an interaction between UIC and MetS in participants aged < 60 years and ≥ 60 years, and no association between UIC and MetS in older participants aged ≥ 60 years. Conclusion: Our study validated the relationship between UIC and MetS and their components in US adults. This association may provide further dietary control strategies for the management of patients with metabolic disorders.

A method of regulating the wind field to reduce safety hazards of gas and dust in fully mechanized heading face based on dynamic data.

Accumulation of gas and dust in excavation work is a safety risk that remains to be solved. A substantial amount of gas and dust accumulate in fully mechanized heading face outlets, and the press-in tube jet cannot be adjusted dynamically based on the actual physical conditions. To solve the problem, a dynamic data-driven method for optimising gas and dust distribution by regulating the wind field is proposed. This method is based on the immune genetic algorithm and uses dynamic data as the incremental data with the historical data from the mine regulation rules to obtain the optimal incremental regulation rules (IRRs) for the wind field. The experiment was performed in Ningtiaota coal mine, Yulin city, northern Shaanxi, China. The observed wind velocity and gas concentrations were within the specification range when regulated by IRRs. The dust concentrations at the position of the driver and the average concentrations on the return air side decreased by 64.6 % and 56.5 %, respectively, when the outlet was 5 m from the head-on. When the distance of the outlet from the head-on was 10 m, the dust concentrations at the position of the driver and the average concentrations on the return air side dropped by 42.9 % and 68.6 %, respectively. The results from this study provide measures that would improve safety and efficiency during excavation of fully mechanized heading faces.

Pharmacokinetic Analysis of Diosgenin in Rat Plasma by a UPLC-MS/MS Approach.

Diosgenin, a steroidal sapogenin, has attracted attention worldwide owing to its pharmacological properties, including antitumor, cardiovascular protective, hypolipidemic, and anti-inflammatory effects. The current diosgenin analysis methods have the disadvantages of long analysis time and low sensitivity. The aim of the present study was to establish an efficient, sensitive ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) approach for pharmacokinetic analysis of diosgenin amorphous solid dispersion (ASD) using tanshinone IIA as an internal standard (IS). Male Sprague-Dawley rats were orally administered diosgenin ASD, and orbital blood samples were collected for analysis. Protein precipitation was performed with methanol-acetonitrile (50 : 50, v/v), and the analytes were separated under isocratic elution by applying acetonitrile and 0.03% formic acid aqueous solution at a ratio of 80 : 20 as the mobile phase. MS with positive electron spray ionization in multiple reaction monitoring modes was applied to determine diosgenin and IS with m/z 415.2⟶271.2 and m/z 295.2⟶277.1, respectively. This approach showed a low limit of quantification of 0.5 ng/ml for diosgenin and could detect this molecule at a concentration range of 0.5 to 1,500 ng/ml (r = 0.99725). The approach was found to have intra- and inter-day precision values ranging from 1.42% to 6.91% and from 1.25% to 3.68%, respectively. Additionally, the method showed an accuracy of -6.54 to 4.71%. The recoveries of diosgenin and tanshinone IIA were 85.81-100.27% and 98.29%, respectively, with negligible matrix effects. Diosgenin and IS were stable under multiple storage conditions. Pharmacokinetic analysis showed that the C max and AUC0⟶t of diosgenin ASD were significantly higher than those of the bulk drug. A sensitive, simple, UPLC-MS/MS analysis approach was established and used for the pharmacokinetic analysis of diosgenin ASD in rats after oral administration.

Ultrasound-Assisted Extraction of Flavonoids from Potentilla fruticosa L. Using Natural Deep Eutectic Solvents.

A series of natural deep eutectic solvents (NADESs) were prepared with choline chloride, betaine, and a variety of natural organic acids in order to find new environmentally-friendly green solvents to replace the traditional solvents. The NADESs were employed to extract flavonoids from Potentilla fruticosa L. (PFL) with the help of ultrasound. The eutectic solvent diluted with an appropriate amount of water improved the extraction ability of flavonoids due to the decrease of solution viscosity. The microstructure of the raw sample and the samples subjected to ultrasonic bath in different solutions were observed using scanning electron microscope (SEM) to determine the role of the NADESs in the extraction process. The DPPH method and glucose consumption method were used to study the antioxidant and hypoglycemic ability of flavonoid compounds in PFL. Single factor method and response surface methodology (RSM) were designed to analyze the effects of three extraction parameters, including solvent/solid ratio, ultrasonic power, and extraction time, on the extraction yield, antioxidant capacity, and hypoglycemic capacity, and the corresponding second-order polynomial prediction models were established. The optimal extraction conditions for the maximum extraction yield, antioxidant capacity, and hypoglycemic capacity were predicted by RSM, and the reliability of RSM simulation results was verified by a one-off experiment.

The complete chloroplast genome of Dictamnus dasycarpus Turcz. (Rutaceae).

Dictamnus dasycarpus Turcz. 1842 is a medicinal plant of China. Its dry root bark is called BAIXIANPI, which is a common traditional Chinese medicine. Here, we report the complete chloroplast genome of D. dasycarpus. The length of the genome, large single-copy (LSC), small single-copy (SSC), inverted repeat (IR), and GC content was 157,056 bp, 84,497 bp, 18,487 bp, 27,036 bp, and 38.5%, respectively. A total of 132 genes were annotated, including 87 protein coding, eight rRNA, and 37 tRNA genes. Interestingly, 15 genes contained single intron while two others contained two introns. The phylogenetic tree showed the two D. dasycarpus (D. albus) clustered in a clade, which was sister to clade formed by the species of Melicope, Tetradium, Phellodendron, and Zanthoxylum.

Long-term prognostic value of macrophage migration inhibitory factor in ST-segment elevation myocardial infarction patients with metabolic syndrome after percutaneous coronary intervention.

Metabolic syndrome (MetS) is a major risk factor for cardiovascular disease and negatively affecting the prognosis of patients with ST elevation myocardial infarction (STEMI). Macrophage migration inhibitory factor (MIF) is a multipotent cytokine involved in various cardiovascular and inflammatory diseases. In this prospective study, we investigate the value of MIF in the long-term prognosis of STEMI combined with MetS after emergency PCI. Circulating MIF levels were measured at admission, and major adverse cardiovascular and cerebrovascular events (MACCE) were monitored during the follow-up period of 4.9 (3.9-5.8) years. MACCE occurred in 92 patients (22.9%), which was significantly higher in MetS (69/255, 27.1%) than in the non-MS subgroup (23/146, 15.8%, P < 0.05). Patients with MetS developed MACCE had the highest admission MIF level. Kaplan-Meier survival analysis using the cutoff value of admission MIF (143 ng/ml) showed that patients with a higher MIF level had a greater incidence of MACCE than those with lower MIF levels in both the MetS (P < 0.0001) and non-MetS groups (P = 0.016). After adjustment for clinical variables, the value of MIF ≥ 143 ng/ml still had the predictive power for the MetS group [HR 9.56, 95% CI (5.397-16.944),P < 0.001]; nevertheless, it was not the case in the non-MetS group. Our findings indicated that MetS is a critical risk factor for adverse clinical outcomes in patients with STEMI, and a high admission MIF level has predictive power for the long-term MACCE, which is superior in STEMI patients with MetS and better than other traditional predictors.

Numerical Investigation of the Influence of Ultimate-Strength Heterogeneity on Crack Propagation and Fracture Toughness in Welded Joints.

The mechanical properties of dissimilar metal-welded joint materials are heterogeneous, which is an obstacle to the safety evaluation of key welded structures. The variation of stress-strain conditions at the crack tip caused by mismatch of material mechanical properties in dissimilar metal-welded joints is an important factor affecting crack propagation behavior. To understand the influence of uneven distribution of ultimate strength of the base metal and the welded metal on the crack propagation path, fracture toughness, as well as the mechanical field at the crack tip in the small-scale yield range, the user-defined field variable subroutine method is used to express continuous variation characteristics of welded joint ultimate strength in finite element software. In addition, the J-integral during crack propagation is calculated, and the effect of the ultimate strength on the J-integral and the stress field at the crack tip are analyzed. The results show that as the crack propagation direction is perpendicular to the direction of ultimate strength, the gradient of ultimate strength increases from |Gy|= 50 to |Gy|= 100 MPa/mm, the crack deflection angle increases by 0.018%, and the crack length increases by 1.46%. The fracture toughness of the material decreased slightly during crack propagation. Under the condition that the crack propagation direction is the same as the direction of ultimate strength, the crack propagation path is a straight line. As the gradient of ultimate strength increases from Gx = 50 to Gx = 100 MPa/mm, the crack propagation length decreases by 5.17%, and the slope of fracture toughness curve increases by 51.63%. On the contrary, as the crack propagates to the low ultimate strength side, the crack propagation resistance decreases, the ultimate strength gradient increases from Gx = -100 to Gx = -50 MPa/mm, and the slope of the fracture toughness curve decreases by 51.01%. It is suggested to consider the relationship between crack growth behavior and ultimate strength when designing and evaluating the structural integrity of cracks at the material interface of dissimilar metal-welded joints.

The complete chloroplast genome sequence of Convallaria majalis L.

The complete chloroplast genome of an important medicinal plant, Convallaria majalis Linnaeus, was sequenced for the first time. The entire circular genome is 162,218 bp in length, with 37.9% GC contents. The genome has consisted of a large single-copy region (LSC) with a length of 85,417 bp, a small single-copy region (SSC) with a length of 18,495 bp, and two inverted repeat regions (IRs) with a length of 29,153 bp each. The genome harbored 133 genes, including 87 protein coding genes, 38 tRNA genes, and eight rRNA genes. The phylogenetic tree of 24 plant species was constructed based on the maximum-likelihood method. This study will provide theoretical basis for further study on plant genetics phylogenetic research.

Long noncoding RNA MALAT1 polymorphism predicts MACCEs in patients with myocardial infarction.

BACKGROUND: Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) participates in the occurrence and development of cardiovascular and cerebrovascular diseases such as stroke and coronary heart disease by regulating inflammatory reactions, programmed cell death, and other pathological processes. Previous studies revealed that the MALAT1 gene polymorphism was associated with cardiac and cerebrovascular diseases. However, the prognostic role of the MALAT1 polymorphism in major adverse cardiac and cerebrovascular events (MACCEs) remains unknown. Therefore, this study intends to explore the association between the MALAT1 rs3200401 polymorphism and MACCEs. METHOD: We enrolled 617 myocardial infarction (MI) patients and 1125 control participants who attended the First Affiliated Hospital of Xinjiang Medical University from January 2010 to 2018. SNPscan™ typing assays were used to detect the MALAT1 rs3200401 genotype. During the follow-up, MACCEs were recorded. Kaplan-Meier curves and univariate and multivariate Cox survival analyses were used to explore the correlation between MALAT1 gene polymorphisms and the occurrence of MACCEs. RESULTS: Among the total participants and MI patients, the frequencies of the T allele (total Participants 19.5% vs. 15.3%, P = 0.047, MI patients 20.7% vs. 14.1%, P = 0.014) and CT + TT genotypes (total Participants 37.4% vs. 28.1%, P = 0.013, MI patients 39.5% vs. 25.8%, P = 0.003) were significantly higher in subjects with MACCEs than in subjects without MACCEs. However, in control participants, the frequencies of the T allele (16.6% vs. 16.0%, P = 0.860) and CT + TT genotypes (31.4% vs. 29.3%, P = 0.760) were not higher in subjects with MACCEs than in subjects without MACCEs. In addition, among the total participants and MI patients, the Kaplan-Meier curve analysis indicated that the subjects with rs3200401 CT + TT genotypes had a higher incidence of MACCEs than CC genotype carriers (P = 0.015, P = 0.001). Nevertheless, similar results were not observed in the control participants (P = 0.790). Multivariate Cox regression indicated that compared with patients with the CC genotype, patients with CT + TT genotypes had a 1.554-fold increase in MACCE risk (hazard ratio: 1.554, 95% confidence interval: 1.060-2.277, P = 0.024). CONCLUSIONS: The MALAT1 rs3200401 CT + TT genotypes could be a risk factor for MACCEs in MI patients, suggesting that the MALAT1 gene may become a biomarker for poor prognosis in MI patients.

The complete chloroplast genome sequence of Veratrum nigrum L.

The complete chloroplast genome of an important medicinal plant, Veratrum nigrum Linnaeus, was sequenced. The entire circular genome is 151,580 bp in length, with 37.7% GC contents. The genome has a large single-copy (LSC) region with a length of 81,806 bp, a small single-copy (SSC) region with a length of 17,472 bp, and two inverted repeat regions (IRs) with a length of 26,151 bp. It harbored 131 genes, including 85 protein coding genes, 38 tRNA genes, and eight rRNA genes. Phylogenetic analysis suggested V. nigrum formed a monophyletic clade with relatively short genetic distance to Veratrum oxysepalum and Veratrum taliense. This study will provide theoretical basis for further study on plant genetics phylogenetic research.

α-Mangostin Treats Early-Stage Adjuvant-Induced Arthritis of Rat by Regulating the CAP-SIRT1 Pathway in Macrophages.

BACKGROUND: Studies have found that α-mangostin (MG) can relieve experimental arthritis by activating cholinergic anti-inflammatory pathway (CAP). It affects the polarization of macrophages and the balance of related immune cell subpopulations, but the specific mechanism is still unclear. It has been found that silent information regulator 1 (SIRT1) is closely related to macrophage activity. The purpose of this study is to explore the mechanism of MG intervening in macrophage polarization during treatment of early adjuvant-induced (AIA) rats through the CAP-SIRT1 pathway. METHODS: We investigated the polarization of M1 macrophages and the differentiation of Th1 in AIA rats by flow cytometry. Activity of acetylcholinesterase (AChE) and the level of nicotinic adenine dinucleotide (NAD+) in serum were also detected, and immunohistochemical was used to detect the levels of α7 nicotinic cholinergic receptor (α7nAChR) and SIRT1. Then in macrophages, the molecular mechanism of MG regulating the abnormal activation of macrophages in rats with early AIA through the CAP-SIRT1 pathway was studied. RESULTS: MG can significantly inhibit the polarization of M1 macrophages and the differentiation of Th1 in AIA rats in the acute phase of inflammation. MG can significantly inhibit the activity of AChE and increase the level of NAD+, thereby further up-regulated the expression levels of α7nAChR and SIRT1. Meanwhile, MG inhibited nuclear factor-κB (NF-κB)-mediated inflammation by activating the CAP-SIRT1 pathway in macrophages. CONCLUSION: In summary, the stimulation of MG induced CAP activation, which up-regulated SIRT1 signal, and thereby inhibited M1 polarization through the NF-κB pathway, and improved the pathological immune environment of early-stage AIA rats.

Interstitial lung disease in Primary Sjögren's syndrome.

BACKGROUND: Interstitial lung disease (ILD) may cause life-threatening complications of primary Sjogren's syndrome (pSS), and has a poor prognosis in terms of survival and quality of life. To date, few studies have investigated the risk factors for ILD detected by high-resolution computed tomography (HRCT) in pSS patients with or without respiratory symptoms. METHODS: Data of 333 patients with newly diagnosed pSS were retrospectively analysed. Interstitial lung disease involvement was defined as typical abnormalities on HRCT and/or pulmonary function tests. Multivariate regression model was used to evaluate the association between interstitial lung disease and pSS characteristics. RESULTS: Sixty-six patients (19.82%) were diagnosed with pSS-ILD. Ground glass opacities (87.88%) and septal/sub pleural lines (81.82%) were most frequent. Based on pulmonary high-resolution computed tomography, patients were divided into nonspecific (n = 42), usual (n = 20), lymphocytic interstitial pneumonia (n = 3) and cryptogenic organising pneumonia (n = 1) groups. There was a strong association between erythrocyte sedimentation rate (ESR)/C-reactive protein (CRP) and the HRCT-score. Pulmonary function tests revealed impaired diffusion capacity for carbon monoxide and total lung capacity, and coexistence of small airway lesions in pSS-interstitial lung disease. On logistic regression analysis, age, Raynaud's phenomenon, lymphopenia, cough, dyspnoea and rampant dental caries were risk factors associated with pSS-interstitial lung disease. CONCLUSIONS: Interstitial lung disease involvement in pSS is a common clinical occurrence. The clinical manifestation is nonspecific and variable; Raynaud's phenomenon and lymphopenia may predict its onset. pSS patients with advanced age, dry cough and dyspnoea should be systematically evaluated for ILD involvement and managed according to their symptoms.

Novelties on the genus Vaccinium (Ericaceae) from Hainan, China: a new species and a new record for the country.

Here we describe a new species, Vacciniumpseudopubicalyx, and report a new record for the flora of China, V.viscifolium, both from Hainan Province. Vacciniumviscifolium also represents the first record of V.sect.Euepigynium for China. Detailed descriptions and illustrations with analytical photographs of the two taxa are provided.

Erythroxylumaustroguangdongense (Erythroxylaceae), a new species from Guangdong, China.

Erythroxylumaustroguangdongense (Erythroxylaceae), a new species from Guangdong Province, China, is described and illustrated. This new species is morphologically most similar to E.calyptratum, but is distinguished by the leathery leaf blade with fewer pairs of secondary veins and flowers borne on leafless nodes of the basal part of the current branch with much longer pedicels and sub-rectangular petal appendages. This is the second native species of Erythroxylum recorded from China.

Effect of Material Heterogeneity on Environmentally Assisted Cracking Growth Rate of Alloy 600 for Safe-End Welded Joints.

Environmentally assisted cracking (EAC) is essential in predicting light water reactors' structural integrity and service life. Alloy 600 (equivalent to Inconel 600) has excellent corrosion resistance and is often used as a welding material in welded joints, but material properties of the alloy are heterogeneous in the welded zone due to the complex welding process. To investigate the EAC crack growth behavior of Alloy 600 for safe-end welded joints, the method taken in this paper concerns the probability prediction of the EAC crack growth rate. It considers the material heterogeneity, combining the film slip-dissolution/oxidation model, and the elastic-plastic finite element method. The strain rate at the crack tip is a unique factor to describe the mechanical state. Still, it is challenging to accurately predict it because of the complicated and heterogeneous material microstructure. In this study, the effects of material heterogeneity on the EAC crack growth behavior are statistically analyzed. The results show that the material heterogeneity of Alloy 600 can not be ignored because it affects the prediction accuracy of the crack growth rate. The randomness of yield strength has the most influence on the EAC growth rate, while Poisson's ratio has the smallest.

Effect of Yield Strength Distribution Welded Joint on Crack Propagation Path and Crack Mechanical Tip Field.

Due to the particularity of welding processes, the mechanical properties of welded joint materials, especially the yield strength, are unevenly distributed, and there are also a large number of micro cracks, which seriously affects the safety performance of welded joints. In this study, to analyze the effect of the uneven distribution of yield strength on the crack propagation path of welded joints, other mechanical properties and residual stresses of welded joints are ignored. In the ABAQUS 6.14 finite element software, the user-defined field (USDFLD) subroutine is used to define the unevenly distributed yield strength, and extended finite element (XFEM) is used to simulate crack propagation. In addition, the static crack finite element model of the welded joint model is established according to the crack propagation path, which is given the static crack model constant stress intensity factor load, and the influence of an uneven yield strength distribution on mechanical field is analyzed. The results show that the crack length of welded joints as well as the plastic deformation range of the crack tip in high stress areas can be reduced with the increase of yield strength along the crack propagation direction. Moreover, the crack deflects to the low yield strength side. This study provides an analytical reference for the crack path prediction of welded joints.