Procedia Engineering最新文献

Selective Laser Melting (SLM) and Electron Beam Melting (EBM) are powder bed fusion processing which allows to build-up parts by successive addition of layers using 3D-CAD models. Among the advantages, are the high degree of freedom for part design and the small loss of material, which explain the increase of Ti-6Al-4V parts obtained by these processes. However, Ti-6Al-4V parts produced by SLM and EBM contain defects (surface roughness, porosity, tensile residual stresses) which decrease significantly the High Cycle Fatigue (HCF) life. In order to minimize the porosity and tensile residual stresses, post-processing treatments like Hot Isostatic Pressing (HIP) and Stress Relieving are often conducted. But the modification of the surface roughness by machining is very costly and not always possible, especially for parts with complex design. The aim of this work is to evaluate the effect of the surface roughness and microstructure of Ti-6Al-4V parts produced by SLM and EBM on the HCF life. Five sets of specimens were tested in tension-compression (R=-1; f=120Hz): Hot-Rolled (reference); SLM HIP machined; SLM HIP As-Built; EBM HIP machined; EBM HIP As-Built. For each condition, microstructure characterization, observation of the fracture surface of broken specimens and surface analysis were carried out respectively by Optical Microscope (OM), Scanning Electron Microscope (SEM) and 3D optical profilometer. Results of fatigue testing show a significant decrease of the HCF life mainly due to the surface roughness. Along with experimental testing, numerical simulations using FEM were conducted using the surface scans obtained by profilometry. Based on extreme values statistics of the crossland equivalent stress averaged on a critical distance, a methodology is proposed to take into account the effect of the surface roughness on the HCF life.

The fire field simulation tool FDS is used to simulate and compare the different fans operating conditions of the semi-transverse ventilation of the proposed Nantong Seyuan Road Tunnel. The fire source is located at the most unfavorable position of the main road and the ramp. The heat release rate is 20 MW and the grid size is 0.2 m. Considering the natural wind speed of 1 m / s and 2 m / s, the air volume of the single fan is 20 m³ / s. The results showed that: (1) The flue gas temperature at the ceiling above the fire sources of all conditions was significantly higher than 100 ℃; when from the fire source area more than 10 m, the CO concentration was not more than 100 ppm and the height of the smoke layer was more than 2 m; (2) Opening the air feed fans was not conducive to reduce the flue temperature at the safe height. (3) Increasing the number of exhaust fans on both sides of the fire source was conducive to flue gas emissions; (4) when the exhaust fans were turned on, the addition of the ramp jet fan can not be significantly to reduce the flue gas temperature at the ramp. The aim of this study is to provide a theoretical basis for the optimization of the semi-transverse ventilation model of the fire in the Nantong Seyuan Road Tunnel.

Implant fixation via the use of acrylic bone cement is now a well-established practice in orthopaedics. Excellent long-term clinical results are evidenced in national joint registers based on over 5 decades of clinical experience. Increased life expectancies, patient BMI, together with the need to remain active in later life, are expected to put greater demands on the materials used in load bearing joint arthroplasty. Failure of bone cement and its interfaces with the implant and bone often leads to loosening, requiring revision surgery. This is a particularly invasive procedure, with lower long-term success rates compared to the primary procedure. To reduce the incidence of bone cement failure, it is necessary to understand the origins of failure in vivo. In the past, bulk failure of bone cement has been attributed to damage accumulation originating at pores. Advances in imaging technology now mean that we are able to observe cement microconstituents readily and identify crack-initiating defects more precisely as we attempt to understand origins of failure. The role of radiopacifier particles within the bone cement has not been examined extensively to date, and the present study demonstrates that this microconstituent could be in crack formation due in part to its ability to agglomerate and not bond with the surrounding matrix. To verify this hypothesis, explanted bone cement and laboratory tested bone cement are compared and correlations in failure mechanisms are discussed.

We focus on applications from the automotive industry, on mechanical components submitted to vibration loads. On one hand, the characterization of loading for dimensioning new structures in fatigue is enriched and updated by customers data analysis. In a second hand, the loads characterization also aims to provide robust specifications dedicated to the simulation or test rigs. We aim to provide vibration specifications that are adapted to a calculation time or physical test durations in accordance with the pace imposed by the projects timeframe. The vibration specifications need to be robust by taking care of the diversity of vehicles and markets considered in the projects. In the trucks industry, the dynamic behavior can vary significantly from one configuration to another. For non-stiff structures, the lifetime depends, among other things, on the frequency content of the loads, as well as the interactions between the components of the multi-input loads. In this context, this paper proposes to compare sets of multi-input loads applied on the non-stiff structure, i.e for which the frequency content of loads impacts the damage.

This study focused on the Disaster Risk Reduction and Management of Tarlac City. The city disaster risk reduction and management structure; the identified hazards and evacuation areas; the Tarlac City DRRM Plan in four thematic areas as identified in the NDRRM Plan; the CDRRMO vehicles, equipment, and resources; and the community based responders are presented in this paper.

The following conclusions are reached based on the gathered information and data. The CDRRMC and CDRRMO are established and functioning as to their mandate, based on the certificate of recognition given by DILG to the City Government of Tarlac regarding disaster preparedness. The structure of the CDRRMO is approved by the city council but lacks funding for filling up the identified positions. The CDRRMO has a hazard map with identified barangays prone to flooding, lahar flow, and earthquake. The thematic action plans of the City Government are aligned with the Sendai Framework for Disaster Risk Reduction. This is evident in the list of programs and projects in their action plans. The existence of community based responders shows that the City Government is extending support to the barangay level by training local officials on how to respond in times of disaster.

The province of Tarlac in the Philippines is one of the commonly flooded areas due to its geographical characteristics. The province is surrounded by high mountains along its eastern and western outskirts but predominantly the province is a vast flat area.

The present study focuses on the development of flood model for the urban areas of Tarlac City wherein a flood overlay zone is developed based on the flood hazard model. Specifically, the study focuses on attaining the following objectives: to develop a flood inundation model; to determine the hazards on the existing land use as well as determine the susceptibility to flood hazard and determine the risks on the urban barangays; and to look into the implications of land use policies towards risk management.

Historical, analytical and qualitative methods were employed to attain the objectives of the study. Stakeholders in the City Disaster Risk Reduction and Management Council (CDRRMC) were involved in the formulation of policies and strategies which may lessen the flood hazards as well as the risks towards the urban communities. The outcome of the workshop will be incorporated to the updated comprehensive land use plan (CLUP) of Tarlac City.

To evaluate fire risk of typical liquid oils applied in nacelle of wind turbine, pyrolysis properties prior to combustion should be known. Pyrolysis properties of three kinds of typical oils of hydraulic oil, gearbox oil and transformer oil were studied by using Thermogravimetry (TG)- Differential Scanning Calorimetry (DSC) technique. Pyrolysis kinetics was analyzed. Apparent activation energy and pre-exponential factor were calculated by using Kissinger method. Results show that according to the TG-DSC analysis, for all three oils, the pyrolysis processes can be divided into three stages. The first stage is evaporation from room temperature to 140.1 °C (gearbox oil), 123.4 °C (transformer oil), and 144.1 °C (hydraulic oil). The second stage is the primary mass loss stage, corresponding temperature is in the range of 140.1–542.0 °C (gearbox oil), 123.4–294.1 °C (transformer oil), and 144.1–329.5 °C (hydraulic oil), among which the temperature of maximum heat mass loss rate of gearbox oil, transformer oil and hydraulic oil is 402.6, 220.1 and 262.6 °C. The third stage is the end of char oxidation and mass of residual char is kept constant, the temperature is higher than 542.0, 294.1, and 329.5 °C. Activation energies and pre-exponential factors were obtained by kinetic analysis, according to the pyrolysis kinetics analysis, the hydraulic oil is more prone to be pyrolyzed than gearbox oil and transformer oil and this provides a basis for judging the combustion characteristics of oil products by pyrolysis kinetic parameters in the future.

In natural disaster and man-made conflict scenarios, livelihoods, assets, community networks and relationships get destroyed and in many areas, lives and communities are devastated. Re-settling these communities and providing them the essential support to adapt to the new or changed environments has been a major challenge for governments. Taking into consideration case studies from two South Asian countries, Bangladesh and Sri Lanka, this paper explores the displacement and re-location cycle experienced and the impact disaster, conflict and reconciliation has on families, community and stakeholder relationships and networks as they re-build their lives in the re-settlement process. The case studies were selected from available literature to focus on different kinds of natural disasters and civil conflicts. The paper focuses on characteristics of resilient communities and how these characteristics have aided the recovery and re-settlement. It also identifies attributes that are inherent in communities that have undergone disaster and displacement and explores how these attributes have helped communities in re-building their lives. From the literature and the case study results and information, it is seen that topics of safety, security, and livelihoods summarises the core needs that are important for transitional settlement and shelter. Having ownership of assets, a shelter or dwelling unit or land is also important in the re-settlement process. These requirements vary according to the ethnicity, religion and culture and the challenges for the relief agencies are to provide alternative solutions that match these requirements in the short and long term.