Servo press forming machines are advanced forming systems that are capable of imparting interrupted punch motion, resulting in enhanced room temperature formability. The exact mechanism of the formability improvement is not yet established. The contribution of interrupted motion in the ductility improvement has been studied through stress relaxation phenomena in uniaxial tensile (UT) tests. However, the reason for improved formability observed when employing servo press is complicated due to the additional contribution from frictional effects. In the present work, an attempt is made to decouple the friction effect on formability improvement numerically. The improved formability is studied using a hole expansion test (HET). The limit of forming during hole expansion is modeled using the Hosford-Coulomb (HC) damage criteria, which is implemented as a user subroutine in a commercial explicit finite element (FE) software. Only the contribution of stress relaxation is accounted for in the evolution of the damage variable during interrupted loading. Therefore, the difference between simulation and experimental hole expansion ratio (HER) can be used to decouple the friction effect from the overall formability improvement during hole expansion. The improvement in HER due to stress relaxation and friction effect is different. The study showed that the model effectively captures the hole expansion deformation process in both monotonic and interrupted loading conditions. Compared to stress relaxation, friction effect played a major role during interrupted HET.
<!--[if gte mso 9]><xml> <o:OfficeDocumentSettings> <o:RelyOnVML/> <o:AllowPNG/> </o:OfficeDocumentSettings> </xml><![endif]--><p class="MsoNormal" style="text-align: justify; line-height: 150%;"><span style="font-size: 12.0pt; line-height: 150%; font-family: 'Times New Roman','serif'; color: black; mso-themecolor: text1;" lang="EN-IN">Background: This study aims to investigate the relationship between carotid intima-media thickness and clinical and metabolic correlation in rheumatoid arthritis (RA) patients.</span></p><p class="MsoNormal" style="text-align: justify; line-height: 150%;"><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 12.0pt; line-height: 150%; font-family: 'Times New Roman','serif'; color: black; mso-themecolor: text1;" lang="EN-IN">Materials and methods</span></strong><span style="font-size: 12.0pt; line-height: 150%; font-family: 'Times New Roman','serif'; color: black; mso-themecolor: text1;" lang="EN-IN">: In this prospective observational case control study, which included 34 patients with RA having disease duration of more than 5 years were compared to 34 healthy matched controls. <br /></span></p><p class="MsoNormal" style="margin-bottom: .0001pt; text-align: justify; line-height: 150%; mso-layout-grid-align: none; text-autospace: none;"><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 12.0pt; line-height: 150%; font-family: 'Times New Roman','serif'; color: black; mso-themecolor: text1;" lang="EN-IN">Results:</span></strong><span style="font-size: 12.0pt; line-height: 150%; font-family: 'Times New Roman','serif'; color: black; mso-themecolor: text1;" lang="EN-IN">The mean age of each cohort and control groups were 48±14.4 and 48.6±14.0 respectively with female preponderance in the study group. Both the groups were comparable for various atherogenic biochemical risk indices like body mass index (BMI), systolic and diastolic blood pressure, random blood sugar, and lipid profile. The study group had a significant elevation of CRP as compared to control group (88% vs 15%). The mean CIMT of study group was 0.86 ± 0.18 and that of control group was 0.53 ± 0.15 and which is statistically significant (p<0.0001). As the severity of disease increases according to disease activity score (DAS 28), the CIMT in study group also showed increasing trend. </span></p><p class="MsoNormal" style="text-align: justify; line-height: 150%;"><strong style="mso-bidi-font-weight: normal;"><span style="font-size: 12.0pt; line-height: 150%; font-family: 'Times New Roman','serif'; color: black; mso-themecolor: text1;" lang="EN-IN">Conclusion</span></strong><span style="font-size: 12.0pt; line-height: 150%; font-family: 'Times New Roman','serif'; color: black; mso-themecolor: text1;" lang="EN-IN">: Rheumatoid Arthritis is a chronic manageable disease with various musculoskeletal morbidities and cardiovascular complications because of chronic subclinical inflammatory state. <br /></span></p><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves/> <w:TrackFormatting/> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> 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Uncoupled ductile fracture models have gained popularity for accurate prediction of fracture in ductile metallic sheets due to their ease of implementation. Accurate description of anisotropic fracture behavior is an active research field for sheet metal forming. In the present study, two isotropic ductile fracture models, i.e., modified Mohr-Coulomb and Hosford-Coulomb are evaluated for an O-tempered aluminum alloy (AA1050-O) sheet. The plastic anisotropy is modeled with a non-associated Hill48 plasticity model. In order to verify the models, experiments are conducted for a 1.2 mm thick AA1050-O sheet under various loading conditions, such as uniaxial tension, in-plane shear, and plane strain tension at room temperature. For evaluating the anisotropic ductile fracture, tensile tests are carried out in 15° intervals to the rolling direction using digital image correlation technique. The predicted fracture limit strains by the two uncoupled fracture models are compared with experimental results to evaluate the accuracy of these models.
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