Correlation of the maximum shear stress with micro-mechanisms of ductile fracture for metals with high strength-to-weight ratio

Lou, Yanshan,Yoon, Jeong Whan,Huh, Hoon,Chao, Qi,Song, Jung-Han Elsevier 2018 International journal of mechanical sciences Vol.146 No.-

<P><B>Abstract</B></P> <P>Mechanisms of ductile fracture are investigated experimentally in a wide range of loading conditions from compressive upsetting to the balanced biaxial tension for two metals with high strength-to-density ratio of DP980 (t1.2) steel sheets and a bulk aluminum alloy of AA7075. Specimens are carefully designed to achieve various loading conditions from shear at low stress triaxiality to the balanced biaxial tension at high stress triaxiality for DP980, while both tensile and compressive tests are conducted for AA7075. Fractured specimen surfaces are analyzed macroscopically focusing on their relations with the maximum shear stress. It is observed that all the specimens tend to fail along the direction of the maximum shear stress in various loading states of plane strain compression, uniaxial compression, shear, uniaxial tension, plane strain tension and the balanced biaxial tension. Scanning electron microscope analyses of fracture surfaces are also conducted to explore the underlying mechanism of void coalescence since coalescence of voids is viewed as the last step of ductile fracture after nucleation and growth of voids. It is noted that fractured voids elongate along the direction of the maximum shear stress for all specimens with the stress triaxiality ranging from about −0.57 in compression to 0.67 in the balanced biaxial tension. The experiments of DP980 and AA7075 reveal that ductile fracture takes place along the direction of the maximum shear stress in the wide loading conditions of compressive upsetting, shear, uniaxial tension, plane strain tension and the balanced biaxial tension with stress triaxiality below 0.67. Thus, ductile fracture is expected to be governed by the maximum shear stress in these wide loading conditions of compression, shear and tension. It is suggested that effect of the maximum shear stress must be correctly coupled in modeling of ductile fracture in these loading conditions with uncoupled and coupled ductile fracture criteria.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mechanisms of ductile fracture is investigated experimentally in the wide range of loading conditions from compressive upsetting to the tension of notched specimens for two lightweight metals of DP980 (t1.2) steel sheets and a bulk aluminum alloy of AA7075. </LI> <LI> All the specimens tend to fail along the direction of the maximum shear stress in various loading states of plane strain compression, uniaxial compression, shear, uniaxial tension and plane strain tension. </LI> <LI> Fractured voids elongate along the direction of the maximum shear stress for all specimens with the stress triaxiality ranging from negative in compression to 0.57 in the plane strain tension. </LI> <LI> The experiments of DP980 and AA7075 reveal that ductile fracture takes place along the direction of the maximum shear stress in the wide loading conditions of compressive upsetting, shear, uniaxial tension, and plane strain tension with stress triaxiality below 0.6. </LI> <LI> Effect of the maximum shear stress must be correctly coupled in modeling of ductile fracture in these loading conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Shear fracture takes place in wide loading conditions of tension, shear and compression. </P> <P>[DISPLAY OMISSION]</P>

Elastodynamic modeling of spatial parallel manipulators contain subclosed loops

Chao Yang,Yang Wang,Junbin Lou,Wei Ye,Fengli Huang 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.3

In this work, the delta parallel manipulator (PM) was considered as a case study to present a system elastodynamic modeling of spatial PMs contain subclosed loops. The mechanism consisted of major substructures including proximal, short, and distal links. Each link was divided into elements to establish the body-to-body and body-to-ground constraint equations. The global independent generalized displacement coordinates (IGDC) of the mechanism were extracted with the theory of multi-point constraint elements. Besides, the global IGDC and substructure synthesis approach was used to obtain the complete elastodynamic modeling of the mechanism without supplementing constraint equations. The resulting configuration-dependent elastodynamic modeling had fewer degrees of freedom, different from thousands used in finite element model (FEM). The natural frequencies could be predicted at any configuration of the mechanism, and were compared against the values of FEM to assess the correctness of the modeling. The proposed modeling could predict the distribution of natural frequencies of the mechanism in the workspace with computational efficiency. Therefore, it could be used as a numerical twin to simulate the elastodynamic performance of PMs in the pre-design stage.

Systemic Inflammatory Biomarkers, Especially Fibrinogen to Albumin Ratio, Predict Prognosis in Patients with Pancreatic Cancer

Lin Fang,Fei-Hu Yan,Chao Liu,Jing Chen,Dan Wang,Chun-Hui Zhang,Chang-Jie Lou,Jie Lian,Yang Yao,Bo-Jun Wang,Rui-Yang Li,Shu-Ling Han,Yi-Bing Bai,Jia-Ni Yang,Zhi-Wei Li,Yan-Qiao Zhang 대한암학회 2021 Cancer Research and Treatment Vol.53 No.1

Purpose Systemic inflammatory response is a critical factor that promotes the initiation and metastasis of malignancies including pancreatic cancer (PC). This study was designed to determine and compare the prognostic value of neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), monocyte-to-lymphocyte ratio (MLR), and fibrinogen-to-albumin ratio (FAR) in resectable PC and locally advanced or metastatic PC. Materials and Methods Three hundred fifty-three patients with resectable PC and 807 patients with locally advan-ced or metastatic PC were recruited in this study. These patients were classified into a training set (n=758) and a validation set (n=402). Kaplan-Meier survival plots and Cox proportional hazards regression models were used to analyze prognosis. Results Overall survival (OS) was significantly better for patients with resectable PC with low preoperative PLR (p=0.048) and MLR (p=0.027). Low FAR, MLR, NLR (p < 0.001), and PLR (p=0.003) were significantly associated with decreased risk of death for locally advanced or metastatic PC patients. FAR (hazard ratio [HR], 1.522; 95% confidential interval [CI], 1.261 to 1.837; p < 0.001) and MLR (HR, 1.248; 95% CI, 1.017 to 1.532; p=0.034) were independent prognostic factors for locally advanced or metastatic PC. Conclusion The prognostic roles of FAR, MLR, NLR, and PLR in resectable PC and locally advanced or metastatic PC were different. FAR showed the most prognostic power in locally advanced or metastatic PC. Low FAR was positively correlated with OS in locally advanced or metastatic PC, which could be used to predict the prognosis.

Chemical constituents from Phyllanthus emblica and the cytoprotective effects on H2O2-induced PC12 cell injuries

Yao Zhang,Lijuan Zhao,Xiaojiang Guo,Chao Li,Haizhen Li,Hongxiang Lou,Dong-Mei Ren 대한약학회 2016 Archives of Pharmacal Research Vol.39 No.9

Two new compounds (1–2), including a bisabolane-type sesquiterpenoid (1), one new diphenyl ether derivative (2), together with 23 known compounds (3–25), were isolated from the fruits of Phyllanthus emblica. Their structures were elucidated by detailed spectroscopic analysis. All the isolated compounds were screened for the DPPH scavenging effects and cytoprotective effects against H2O2 induced PC12 cells injury. Compounds 12–15 showed significant DPPH scavenging effects with the IC50 values in the range of 3.25–4.18 lM. Among these potential antioxidants, compound 14 improved the survival of PC12 cells after H2O2 exposure without showing any cytotoxicity at the tested concentrations.

Simplified method for prediction of elastic-plastic buckling strength of web-post panels in castellated steel beams

Mei Liu,Kangrui Guo,Peijun Wang,Chao Lou,Yue Zhang 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.25 No.6

Elastic-plastic shear buckling behaviors of the web-post in a Castellated Steel Beam (CSB) with hexagonal web openings under vertical shear force were investigated further using Finite Element Model (FEM) based on a sub-model, which took the upper part of the web-post under horizontal shear force to represent the whole web-post under vertical shear force. A simplified design method for the web-post elastic-plastic shear buckling strength was proposed based on simulation results of the sub-model. Proper boundary conditions were applied to the sub-model to assure that its behaviors were identical to those of the whole web-post. The equation to calculate the thin plate elastic shear buckling strength was adopted as the basic form to build the design equation for elastic-plastic buckling strength of the sub-model. Parameters that might affect the elastic-plastic shear buckling strength of the whole web-post were studied. After obtaining the vertical shear buckling strength of a sub-model through FEM, the shear buckling coefficient k can be obtained through the back analysis. A practical calculation method for k was proposed through curving fitting the parameter study results. The elastic-plastic shear buckling strength of the web-post calculated using the proposed shear buckling coefficient k agreed well with that obtained from the FEM and test results. And it was more precise than those obtained from EC3 based on the strut model.

PTEN mutation predicts unfavorable fertility preserving treatment outcome in the young patients with endometrioid endometrial cancer and atypical hyperplasia

Yu Xue,Youting Dong,Yaochen Lou,Qiaoying Lv,Weiwei Shan,Chao Wang,Xiaojun Chen 대한부인종양학회 2023 Journal of Gynecologic Oncology Vol.34 No.4

Objective: This study aimed to investigate the impact of molecular classification and PTEN, KRAS and PIK3CA gene mutation on the outcome of fertility-preserving treatment in the patients with endometrioid endometrial cancer (EEC) and endometrial atypical hyperplasia (EAH). Methods: This is a single-center retrospective study. A total of 135 patients with EEC and EAH receiving fertility-preserving treatment and molecular classification were reviewed. The distribution of the four types of molecular classification was described. The impact of non-specific molecular profile (NSMP), mismatch repair-deficiency (MMRd), and PTEN, KRAS and PIK3CA gene mutation on the outcome of fertility-preserving treatment was analyzed. Results: Of the patients analyzed, 86.7% (117/136) were classified as having NSMP; 14 (10.4%), MMRd; 1 (0.7%), POLEmut EAH; and 3 (2.2%), p53abn EEC. The patients having NSMP and MMRd achieved similar 16-, 32-, and 48-week complete response rates. The patients harboring tier I and tier II PTEN mutations (PTENmut-Clin) achieved lower cumulative 32-week CR rates than those with PTEN-others (without PTENmut-Clin) (22/47, 46.8% vs. 50/74, 67.6%; p=0.023; odds ratio=0.422; 95% confidence interval [CI]=0.199–0.896). Insulin-resistance (hazard ratio [HR]=0.435; 95% CI=0.269–0.702; p=0.001) and PTENmut-Clin (HR=0.535; 95% CI=0.324–0.885; p=0.015) were independent negative predictors for lower 32-week CR rates. Conclusion: PTENmut-Clin is an independent risk factor for unfavorable fertility-preserving treatment outcomes in the patients with EEC and EAH. The patients with MMRd receiving fertility-preserving treatment achieved outcomes similar to those of the patients with NSMP. The molecular profiles might guide fertility-preserving treatment in the prognosis and clinical decisions.

Mechanical Properties and Energy Absorption of Soft–Hard Dual Phase Lattice Structures Manufactured via Selective Laser Melting

Yi Ren,Yu Nie,Wei Ran,Zhuofan Liu,Lixia Wang,Chao Lou,Wei Chen 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.2

Lattice structures with excellent mechanical performance can be achieved through delicate design. In this work, inspired bythe soft–hard multiphase crystals, three types of dual phase lattice structures (DPLS) composed of body-centered cubic withZ-struts (BCCZ) matrix phase and face and body-centered cubic with Z-struts (FBCCZ) reinforcement phase were designedand fabricated by selective laser melting (SLM) using 316L stainless steel powder. Quasi-static compression experimentand numerical simulation were carried out to investigate their mechanical properties, energy absorption and deformationbehavior. The results showed that the mechanical properties of all DPLS samples were higher than that of single phaseBCCZ lattice structure. The four-body diagonal DPLS sample exhibited the highest specific strength and specific stiffness,which was 9.0% and 14.2% higher than single phase BCCZ lattice structure; while, the two-face diagonal DPLS sample hadthe highest specific energy absorption value of 17.45 J/g. Besides, the experimental and simulated results revealed that thearrangements and volume fraction of reinforcement phase had a significant impact on the performance, deformation behaviorand internal stress distribution of the DPLS samples during compressive deformation.