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

3D Thermal Model of Laser Surface Glazing for H13 Tool Steel

In this work a three dimensional (3D) finite element model of laser surface glazing (LSG) process has been developed. The purpose of the 3D thermal model of LSG was to achieve maximum accuracy towards the predicted outcome for optimizing the process. A cylindrical geometry of 10mm diameter and 1mm length was used in ANSYS 15 software. Temperature distribution, depth of modified zone and cooling rates were analysed from the thermal model. Parametric study was carried out varying the laser power from 200W-300W with constant beam diameter and residence time which were 0.2mm and 0.15ms respectively. The maximum surface temperature 2554°K was obtained for power 300W and minimum surface temperature 1668°K for power 200W. Heating and cooling rates increased with increasing laser power. The depth of the laser modified zone attained for 300W power was 37.5µm and for 200W power was 30µm. No molten zone was observed at 200W power. Maximum surface temperatures obtained from 3D model increased 4% than 2D model presented in author’s previous work. In order to verify simulation results an analytical solution of temperature distribution for laser surface modification was used. The surface temperature after heating was calculated for similar laser parameters which is 1689°K. The difference in maximum surface temperature is around 20.7°K between analytical and numerical analysis of LSG for power 200W

Two dimensional finite element thermal model of laser surface glazing for H13 tool steel

A two dimensional (2D) transient thermal model with line-heat-source was developed by Finite Element Method (FEM) for laser surface glazing of H13 tool steel using commercial software-ANSYS 15. The geometry of the model was taken as a transverse circular cross-section of cylindrical specimen. Two different power levels (300W, 200W) were used with 0.2mm width of laser beam and 0.15ms exposure time. Temperature distribution, heating and cooling rates, and the dimensions of modified surface were analysed. The maximum temperatures achieved were 2532K (2259°C) and 1592K (1319°C) for laser power 300W and 200W respectively. The maximum cooling rates were 4.2×107 K/s for 300W and 2×107 K/s for 200W. Depths of modified zone increased with increasing laser power. From this analysis, it can be predicted that for 0.2mm beam width and 0.15ms time exposer melting temperature of H13 tool steel is achieved within 200-300W power range of laser beam in laser surface glazing

Modelling of Laser Surface Glazing for Metallic Materials by Finite Element Method

Laser surface glazing (LSG) is widely used to improve surface hardness and wear resistance in casting tool, railroad, automotive and bioimplant industries. This PhD project focused on developing a simple and reliable model of LSG for metallic materials by FEM. Both 2D and 3D transient thermal model of LSG with cylindrical geometry were successfully developed in ANSYS mechanical APDL software. Temperature distributions, heating, cooling rates and depth of modified zone of LSG treated parts were predicted from the thermal model. The temperature distribution resulting from thermal model were used to develop a 2D coupled thermomechanical model to predict residual stress for H13 tool steel using two plasticity theories, isotropic and kinematic. The thermal model was conducted for H13 tool steel and Ti6Al4V alloy. The laser power range 200-300 W and 100-200 W were used respectively with constant 0.2 mm beam width and 0.15 ms residence time. Results showed that surface peak temperature increased proportionally with laser power. Heating and cooling rates were extremely high in the range of 106-107 Ks-1 for both alloys and increased with laser power. The depth of modified zone was in micron range and increased with laser power. The parametric study of thermal model determined threshold power level 210 W and 130 W to initiate melting of H13 tool steel and Ti6Al4V alloy respectively. Thermomechanical model showed that tensile residual stress induced in the modified surface of H13 tool steel. Isotropic plasticity model developed higher von Mises residual stress than the kinematic model. Furthermore, the developed thermal model of LSG was applied to simulate quenching and tempering heat treatment of structural steel. The temperature distribution, cooling rates and outer case depth caused by quenching were predicted from the model. The calculated case depth from the model showed good agreement with the measured case depth found in the experimental work

Sustainability assessment of a slum upgrading intervention in Bangladesh

Equitable provision of physical infrastructure must be seen as a prerequisite for achieving the sustainability of human settlements. Infrastructure provision needs to consider both the product (physical services) and the context in which the services will be provided and maintained in order to be sustainable. This article presents a holistic methodology for evaluating sustainability and poverty reduction impact of infrastructure projects in developing countries through societal, economics, institutional and environmental dimensions. ASPIRE toolkit uses qualitative evidence which feeds into 96 indicators producing visual outputs which can encourage users to consider contextual issues and develop valuable trade-offs between the four dimensions.The methodology and toolkit are applied to the evaluation of an infrastructure upgrading project in Korail, Bangladesh. The Urban Partnership for Poverty Reduction Project (UPPRP) in Korail supports a twin-pronged approach of provision of infrastructure (water, sanitation, roads and drainage) improvement through the Slum Improvement Fund and improvement of socio-economic conditions through the Socio-Economic Funds. The ASPIRE assessment allowed the authors to interrogate strengths and weaknesses of the UPPR project thereby demonstrating the value added by ASPIRE. Overall, the project was deemed successful in Korail. Socially, it allowed access to all types of services to the slum's residents with strong community engagement. Land security however was noted to be a challenge, which needs to be addressed by institutions in Dhaka

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

Reactions of Rhenium and Manganese Carbonyl Complexes with 1,8-bis(diphenylphosphino)naphthalene: Ligand Chelation, C–H and C–P bond-cleavage Reactions

Reaction of [Re2(CO)8(MeCN)2] with 1,8-bis(diphenylphosphino)naphthalene (dppn) afforded three mono-rhenium complexes fac-[Re(CO)3(κ1:η1-PPh2C10H6)(PPh2H)] (1), fac-[Re(CO)3{κ1:κ1:η1-(O)PPh2C10H6(O)PPh(C6H4)}] (2) and fac-[ReCl(CO)3(κ2-PPh2C10H6PPh2)] (3). Compounds 1–3 are formed by Re–Re bond cleavage and P–C and C–H bond activation of the dppn ligand. Each of these three complexes have three CO groups arranged in facial fashion. Compound 1 contains a chelating cyclometalated diphenylnaphthylphosphine ligand and a terminally coordinated PPh2H ligand. Compound 2 consists of an orthometalated dppn-dioxide ligand coordinated in a κ1:κ1:η1-fashion via both the oxygen atoms and ortho-carbon atom of one of the phenyl rings. Compound 3 consists of an unchanged chelating dppn ligand and a terminal Cl ligand. Treatment of [Mn2(CO)8(MeCN)2] with a slight excess of dppn in refluxing toluene at 72 °C, gave the previously reported [Mn2(CO)8(μ-PPh2)2] (4), formed by cleavage of C–P bonds, and the new compound fac-[MnCl(CO)3(κ2-PPh2C10H6PPh2)] (5), which has an unaltered chelating dppn and a terminal Cl ligand. In sharp contrast, reaction of [Mn2(CO)8(MeCN)2] with slight excess of dppn at room temperature yielded the dimanganese [Mn2(CO)9{κ1-PPh2(C10H7)}] (6) in which the diphenylnaphthylphosphine ligand, formed by facile cleavage of one of the P–C bonds, is axially coordinated to one Mn atom. Compound 6 was also obtained from the reaction of [Mn2(CO)9(MeCN)] with dppn at room temperature. The XRD structures of complexes 1–3, 5, 6 are reported

Assessment of the dielectric anisotropy in timber using the nondestructive GPR technique

In the realm of architecture ground-penetrating radar has been used as nondestructive technique to assess physical properties of wood structures in situ. However, a better understanding of the dielectric anisotropy of timber is needed to develop this application. An experiment was conducted on samples of sawn timber of different species (densities) to study their dielectric responses according to the grain directions using a GPR with a 1.6 GHz antenna. Interesting differences were found: the propagation velocities, as well as the amplitudes of the direct and reflected waves always presented lesser when the electric field was longitudinal to the grain than when transverse. But when the field was propagated in whatever transverse direction some of those parameters not differ greatly.On the other hand, this work is supported partly by the "Programa de Apoyo a la Investigacion y Desarrollo (PAID-00-11)" of the Universitat Politecnica de Valencia. The authors would like to acknowledge the contribution of Dr Briggs of the School of Forest Resources at the University of Washington, Seattle (USA).Martínez Sala, RM.; Rodríguez Abad, I.; Díez Barra, R.; Capuz Lladró, R. (2013). Assessment of the dielectric anisotropy in timber using the nondestructive GPR technique. Construction and Building Materials. 38:903-911. doi:10.1016/j.conbuildmat.2012.09.052S9039113