Prof. Dr. Ir. Tatacipta Dirgantara

Here, lessons learned during the development of the CPAP ventilator ‘Vent-I’, aimed to help COVID-19 patients with breathing difficulties, are presented. Within only weeks, the Vent-I was developed, complying with functionality, safety and reliability requirements and passing the clinical trial. It was then distributed to hospitals all over Indonesia. Two billion rupiahs were raised through crowdfunding within one week. When the project was officially closed, more than one thousand Vent-I devices had been distributed and more than twelve and a half billion rupiahs had been raised. Currently, commercialization and mass production of the device have been started. From this project several lessons can be learned. First and foremost, the spirit of gotong royong”? sincere collaboration within the community to help each other “? is still firmly rooted within the people and the society of Indonesia. Noble values, i.e. sincerity, sensitivity and concern about the needs of the community, willingness to serve voluntarily and public trust, made the team dare to try and face failure. The spirit of social entrepreneurship, willingness to listen to the user and collaboration with the relevant authority can accelerate development process. The availability of knowledge and skills that constitute an innovation ecosystem in Bandung, supported by business, social institutions and government, was also a key success factor.   Download Preprint | Go To Publisher

This paper presents results on the crushing behavior of aluminum foam–filled columns with square cross section. Here, the effect of inserting an aluminum foam to single–walled and double–walled columns were studied. Parametric study for both types of columns compared with single–walled and double–walled columns were also carried out. In this work, the effect of strain rate of the aluminum foam was considered in the material model. The numerical results were compared with the available experimental data and shown to be in a very good agreement. The models that considered the strain rate effect of foam core gave better predictions compared to the ones without considering the strain rate effect. It will result in higher energy absorption and bigger local deformation on corners resulting a slightly increase of the overall crushing force. It can be said that the strain rate of the foam core plays a quite significant role in crushing behavior of the foam-filled columns, and should be taken into account. The results also showed that the interaction between the foam core and the column wall will change the deformation mode from one localized fold to multiple propagating folds and lead to the increase of total mean crushing force of the column. Similar effect of foam filling was also found in double–walled foam–filled columns. Further investigation has been conducted on the effect of core thickness to the mean crushing force response of the columns. It is also found that increasing the core thickness in double–walled foam–filled column will improve the crushing behavior up to a point where there is still interaction between the walls. After that, the further increase of the core thickness will make the column response approaching the crushing force of single–walled foam–filled.   Download Preprint | Go To Publisher

This paper presents a numerical and experimental study of several configurations of multi-cell columns compared to single-walled and double-walled columns subjected to dynamic axial impact forces. The impact of the columns was numerically analysed using FEM and also verified by experimental testing. The effect of the column mass and thickness of the multi-cell columns compared to single- and double-walled columns was also studied. The results showed that, by analysing a group of columns with the same thickness and weight, the energy absorption efficiency can be significantly improved by introducing internal ribs to the double-walled columns. The results showed that the crushing force of the middle ribs (MR) multi-cell columns was the highest, followed by the corner ribs (CR) multi-cell columns, the double-walled (DW) columns and the single-walled (SW) columns, respectively. © 2014 Elsevier Ltd. All rights reserved.   Download Preprint | Go To Publisher

In this paper, an analytical prediction and numerical simulation of the behavior of square crash box structures having hole at corners on dynamic axial crushing are studied. The focus of the present theoretical prediction is to calculate the mean crushing force and maximum crushing force during the folding process subjected to axial impact loading. Then, the effect of hole size to the crushing response of square crash box structures was also evaluated. For validation, an explicit nonlinear commercial finite element code LS-DYNA was used to predict the response of the structures subjected to axial crushing. It was found that results of numerical method and theoretical prediction were in good agreement. The results showed that, by inserting holes at corners, the folding can be controlled to be always started from the hole, and peak crush load on the first fold can be reduced significantly. Meanwhile, the decreasing of mean crushing force is insignificant compared to the one without holes. Hence, the characteristic of impact energy absorption in a progressive buckling can be improved, the damage in passenger compartment can be minimized, and the deceleration level can be kept in safe level to prevent injury of the passenger. Download Preprint | Go To Publisher

In the present work, the effect of several Digital Image Correlation (DIC) parameters to the accuracy of the Stress Intensity Factors (K), was investigated. The values of Kı and Kıı were estimated in a three point bend specimen from the displacement field values around the crack tip obtained experimentally by using the DIC technique, using non-linear least square technique together with Taylor’s expansion. It was found that some DIC parameters i.e. subset and template area should be carefully chosen in order to obtain an accurate result. The results showed that by setting the subset and the template edge length ratio to be 0.2 – 0.6, the K of mode I and mode II were in good agreements compared to the finite element results. The maximum difference of Kı is 1.9% and Kıı is 4.6%.   Download Preprint | Go To Publisher