Design Optimization of Leaf Spring Using FEM and RSM

The prime objective of this design and analysis work is to design a Pressure vessel by following the standards of American Society of Mechanical Engineers (ASME). Pressure vessel as a subject matter was opted for the design and analysis with a principal aim to minimize the stress being produced within the structure by structural modification in the Pressure vessel by using analytical approach. ASME (BPVC) Sec-VIII Div- I and Div-II was used to follow the Design by Rule (DBR) and Design by Analysis (DBA) approach. Along with that ASME (BPVC) Sec-II Part- A and Part- D was followed. Cylindrical, Horizontal bullet type Pressure vessel with Hemispherical head was used for this analysis .This work was intended for Stress Minimization within the structure as a principal aim, which is being caused by the exertion of pressure of the fluid on the internal wall and for this SA516Gr65 and SA537 CL 1 material was selected form ASTM Library. This designed Pressure vessel to be used for the LPG gas storage under the internal design pressure of 1.55MPa at 55°C. The design and analysis work was carried out in two sections Design by Rule (DBR) which is a conventional design, for that empirical formula was used to calculate the value of stress being produced under the given conditions and for the required thickness of the shell, head and nozzle to sustain the applied pressure of fluid by following the standards of ASME (BPVC) SecVIII Div- I and Deign by Analysis (DBA), which is a analytical design approach, here Finite Element Method (FEM) was opted for the analysis of the designed model, which was done in the CATIA V5, here in the CATIA two models, Model 1 and Model 2 were created and a structural modification was done in the model 2 and then analysis was performed in the Ansys Workbench 16.0. The comparison was made for both the design approach for the minimized stress values of Hoop Stress and Longitudinal Stress by structural modification and the required thickness under the alternative materials selections criteria was discussed. Up to 25% less stress value was seen in comparative structural analysis of Model 1 and Model 2. This report also discusses the use of SA537 CL 1 material as an alternative options which helps to reduce the thickness of the vessel when compared to the existing materials because this material can sustain the same amount of pressure under given condition at a thinner shell also, this is numerically proved here in this work. Keywords: Pressure Vessel, ASME, Stress Minimization, LPG, FEM, DBR, DBA, Optimum Design.

Stress minimization for lattice structures. Part I: Micro-structure design

Lattice structures are periodic porous bodies which are becoming popular since they are a good compromise between rigidity and weight and can be built by additive manufacturing techniques. Their optimization has recently attracted some attention, based on the homogenization method, mostly for compliance minimization. The goal of our two-part work is to extend lattice optimization to stress minimization problems two-dimensionally. The present first part is devoted to the choice of a parametrized periodicity cell that will be used for structural optimization in the second part of our work. In order to avoid stress concentration, we propose a square cell microstructure with a super-ellipsoidal hole instead of the standard rectangular hole often used for compliance minimization. This type of cell is parametrized two-dimensionally by one orientation angle, two semi-axis and a corner smoothing parameter. We first analyse their influence on the stress amplification factor by performing some numerical experiments. Second, we compute the optimal corner smoothing parameter for each possible microstructure and macroscopic stress. Then, we average (with specific weights) the optimal smoothing exponent with respect to the macroscopic stress. Finally, to validate the results, we compare our optimal super-ellipsoidal hole with the Vigdergauz microstructure which is known to be optimal for stress minimization in some special cases. This article is part of the theme issue ‘Topics in mathematical design of complex materials’.

EFFORTS TO MINIMIZE STRESS IN ADOLESCENTS THROUGH GOING FOR COFFEE "NGOPI" IN MALANG CITY

There are a large number of teenagers in the world who experience mental health problems as a result of stress, which disrupts human productivity. A good mental state allows people to realize the potential that exists in themselves, overcome the stresses of life, work productively, and contribute to their community. The purpose of this study was to describe efforts to minimize stress among adolescents by going for coffee in Malang city. This research was descriptive with a quantitative approach. Data was obtained through direct observation and interviews with respondents based on research guidelines. Stress minimization refers to the reduction of stress or actions taken when experiencing stress to calm the mind, which can be done by seeking peace, drinking coffee, and hanging out with friends. Managing stress in adolescents is important because it will affect the next stage of their lives. If adolescents cannot manage stress properly, they will continue to think about it and their performance will not be optimal. The attitude taken when having a problem that disturbs the mind can vary, such as worshipping first then looking for the source of the problem. Alternatively, taking a walk and drinking coffee can calm the mind. Doing assignments in a coffee shop rather than in a boarding house is more productive and allows for many ideas to arise.Keywords: stress, reducing stress, coffee shop, teenage age

Generalized tessellations of superellipitcal voids in low porosity architected materials for stress mitigation

Stress concentration is a crucial source of mechanical failure in structural elements, especially those embedding voids. This paper examines periodic porous materials with porosity lower than 5%. We investigate their stress distribution under planar multiaxial loading, and presents a family of geometrically optimized void shapes for stress mitigation. We adopt a generalized description for both void geometry and planar tessellation patterns that can handle single and multiple voids of arbitrary void shape at a generic angle. The role of void shape evolution from diamond to rectellipse on the stress-distribution is captured at the edge of voids in a representative volume element (RVE) made of non-equal length periodic vectors. Theoretical derivations, numerical simulations along with experimental validation of the strain field in thermoplastic polymer samples fabricated by laser cutting unveil the role of geometric parameters, e.g. superellipse order, aspect ratio and rotation angle, that minimize stress peak and ameliorate stress distribution around voids. This work extends and complements classical theory by providing fundamental insights into the role that tessellation, void shape and inclination play in the stress distribution of low-porosity architected materials, thus introducing essential guidelines of broad application for stress-minimization and failure mitigation in diverse sectors.