3D Thermal Model of Laser Surface Glazing for Ti6Al4V alloy

t: Ti6Al4V alloy plays a significant role in the biomedical applications such as bioimplants for its excellent biocompatibility. Its usage can be further extended by improving the surface hardness and wear resistance. In this respect, laser surface glazing (LSG), an advanced surface modification technique, is very useful which can produce thin hardened surface layer and strong metallurgical bonding. Investigation of temporal and spatial temperature distributions of laser glazed surface of materials are essential because temperature plays significant role in achieving required surface properties. Therefore, in this study, a 3D Finite element analysis has been developed to perform transient thermal analysis of LSG for Ti64 alloy. The model investigated temperature distribution, depth of modified zone and heating and cooling. The results show that the peak temperature is attained 2095 K for 300 W laser power, 0.2 mm beam width and 0.15 ms residence time. Since this temperature is above the melting point (1933 K) of Ti64 alloy, the melt depth is calculated 22.5 μm. Furthermore, from the simulation results, the average heating and cooling rates are estimated 1.19×107 Ks-1 and 2.71×106 Ks-1 respectively which indicate the presence of hard phases in the modified zone

A One-dimensional Analysis of the Distribution of Temperature, Stress and Strain in the co-axial Laser Cladding Process

The co-axial Laser Cladding (LC) is one of the most advanced surface treatment processes where generally a superior powder or wire material is deposited on the substrate to improve surface properties by using laser heat source. In this work, a physical model of the clad and the substrate has been presented. An attempt has been made to describe the simplified relation of temperature, stress and strain with time by using the established theoretical knowledge of generation of stress and strain after thermal treatment. The simplified relation of temperature, stress and strain with time has been explained with the help of schematic diagrams. The finding of this study will help to understand the temperature, stress and strain behaviour with time in the Laser Cladding process

Progress in Numerical Simulation of the Laser Cladding Process

Laser Cladding is one of the developing manufacturing techniques used for diverse applications such as coating, repairing and prototyping. Complex processing phenomena and the formation and growth of thin clad of few micrometers to millimeters range in most cases are yet to be fully understood. However, in recent past, several numerical models have been reported to get some understanding of physical, dynamic and metallurgical phenomena of this process. This article reviews the progress of numerical simulations spanning over three distinct stages of the process to model powder flow dynamics, melt pool and clad properties. For each stage, the governing equations, the effect of process variables and experimental validation techniques have been discussed. Specifically, we have outlined some of the underlying assumptions in the current numerical models which can act as pointers for further improvement of the existing numerical models. Authors recommend that numerical simulation results have to be complemented with experimental results to achieve better clad properties

Study of prevalence of bacterial vaginosis in preterm and term labour patients

Background: Bacterial vaginosis (BV) is a clinical condition caused by replacement of the normal hydrogen peroxide producing Lactobacillus species with high concentrations of aerobic and anaerobic bacteria. Studies have shown that spontaneous abortion, preterm labour (PTL), premature birth, preterm premature rupture of membranes, amniotic fluid infection, and postpartum endometritis are increased because of infection with BV. In India, not many studies have been done to estimate the prevalence and association of BV with preterm labour, hence this study is being taken up to know the prevalence of BV in preterm and term labour patients and its relationship with preterm delivery, low birth weight of baby and puerperal sepsis.The objective of the present study was to observe the prevalence of bacterial vaginosis in women presenting with preterm and term labour, its impact on preterm and term delivery and to analyze the maternal and fetal complications associated with BV.Methods: An observational study involving 100 patients with preterm and term labour (50 patients in each group) was conducted at a BNMCCC, Government Medical College, Amritsar. Women fulfilling the Amsel’s criteria and/or a score of 7 or more on gram staining of vaginal smears (Nugent’s score) was considered to have bacterial vaginosis.Results: The proportion of patients, who fulfilled Amsel’s criteria and/or a Nugent’s score of 7 or more for the diagnosis of BV, was more in PTL group versus term labour group, and the difference was statistically significant. Prevalence of BV in preterm labour and term labour patients was 18(36%) versus 4(8%) respectively. In PTL group, 27.8% of low birth weight neonates were born to BV positive mothers versus 3.1% were born to BV negative mothers. Maternal postpartum complications observed were 33.3% with BV versus 6.25% without BV in PTL group.Conclusions: BV is major risk factor for PTL. Therefore, the testing and prompt treatment of BV may reduce the risk of PTL. This will also go a long way in the prevention of maternal morbidity and neonatal complications due to prematurity

Major Thrombotic Event Despite Anticoagulation in a Patient With COVID-19.

The outbreak of coronavirus disease 2019 (known as COVID-19), which started in Wuhan, China in December 2019, is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has been associated with both venous and arterial thromboembolism likely secondary to significant cytokine activation and inflammation. Reports on the incidence of thrombotic complications, however, are not well documented. Our case will examine a young man diagnosed with COVID-19 who developed an acute, severe bilateral saddle pulmonary embolism while on prophylactic dose anticoagulation after being admitted to the hospital and treated for two weeks with significant improvement

Thermo-mechanical modelling to evaluate residual stress and material compatibility of laser cladding process depositing similar and dissimilar material on Ti6Al4V alloy

The formation of residual stresses due to thermo-mechanical effect and microstructural transformation in the Laser Cladding process predominantly affects the final product integrity and service life. A 3D finite element transient thermo-mechanical model has been developed to predict thermal profile and residual stress distribution for repair application of Ti6Al4V alloy using a moving heat source. Then the developed model was applied for the deposition of ceramic materials Al2O3 and TiC on Ti6Al4V alloy substrate. The outcome of this model is to predict temperature distribution, cooling rate, melt pool depth, heat affected zone and residual stress. This study mainly highlights the thermal effect on the residual stresses for similar and dissimilar clad/substrate materials and suggests the suitable cladding material with minimum residual stress

The advent of system toxicology: aims and aspect of toxicogenomics

Last fifty years a significant advancement has been established in biological science. It happened due to the discovery of gene, genome and genetic code, function of genes and mutation of genes. Through this, the scientists have discovered that genetic code is the building block and fundamental of all molecular activity in biological system. According to this, several molecular techniques have been established to prove molecular events, effects of chemical exposure within individuals and environment. For this evaluation, the necessary of toxicogenomics is crucial, that deals with the effects of chemical in changing the genetic pattern along with mutation into gene. Toxicogenomics also deals with transcription of proteins and metabolite profiling to investigate the interaction of genes and environment stress in disease. Toxicogenomics also described the altered expression of genes caused by mutation and chemical exposure that cause several disease and show toxicant functions in cell. The main objective of toxicogenomics is to remove this exposure and provide remedy of these toxical diseases. The use, application, correlation, combination and collaboration of different significant, major, modern biological fields like proteomics, transcriptomics, bioinformatics, microarray and several other molecular process is carried out by toxicogenomics that gradually evolving in systems toxicology. This review recovered the evolution and significant application of the different fields of toxicogenomics