Numerička analiza čvrstoće šasije ultra sportskih automobila

master's thesis

• Title (english): Numerical analysis of strength of supercar chassis
• Author: Martin Mikulčić
• Mentor: Ivica Skozrit (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2016-01-22, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; General Mechanical Engineering (Construction)

Abstract

Tema rada je numerička analiza čvrstoće okvira ultra sportskih automobila. Točnije, proračun torzijske krutosti okvira automobila Concept One kompanije Rimac Automobili [1].

U uvodu diplomskog rada ukratko je opisana problematika današnjih inženjerskih proračuna. Potom, opisana je kompanija Rimac Automobili koja je trenutno vodeća u razvoju i proizvodnji električnih ultra sportskih automobila te koja je ustupila CAD (eng. Computer-aided Design) model okvira svog automobila Concept One kao predmet analize diplomskog rada. Također, stavljen je kratki osvrt na sam automobil Concept One te su navedene njegove karakteristike.

Kao zasebno poglavlje uvoda, prikazan i opisan je razvoj okvira automobila kroz prošlost te su navedeni kriteriji koje bi jedan okvir automobila trebao zadovoljiti. Zatim je općenito definirana krutost konstrukcije, a detaljnije opisana torzijska krutost konstrukcije. Posebno je analizirana torzijska krutost okvira automobila jer je upravo ona indikator koji dio okvira je možda lošije konstruiran i ima manju krutost od željene, odnosno tražene. Također, vrlo je bitna za upravljivost i postavke ovjesa jer one uvelike utječu na vozne karakteristike automobila.

U sljedećem poglavlju, detaljnije je opisana metoda konačnih elemenata kojom je proračun proveden i koja je zadnjih godina sve popularnija zbog napretka računalne tehnologije jer zahtjeva dosta resursa za provedbu same simulacije. Tu se misli na RAM (eng. Random Access Memory) memoriju te na procesorsku snagu. Zatim je na jednostavnijim i specifičnim primjerima koji su analitički rješivi napravljena verifikacija grednih i ljuskastih konačnih elemenata koji će biti korišteni u proračunskom modelu za rješavanje simulacije programskim paketom ANSYS [2]. Verifikacijom je pokazano da su željeni konačni elementi pogodni za opis proračunskog modela i provedbu numeričke analize.

Nadalje, opisan je postupak kreiranja proračunskog modela koji kreće izradom modela okvira od linija i površina u programskom paketu CATIA [3] te uvozom u programski paket ANSYS u kojem su definirani poprečni presjeci cijevi te debljine ojačanja okvira u vidu limova. Potom je takav proračunski model diskretiziran, nametnuti su mu zadani rubni uvjeti pomaka i sila te je napravljeno i validirano pet različitih mreža konačnih elemenata (od rjeđe do gušće diskretizacije) da bi se ispitala konvergencija rješenja.

Dobiveni rezultati su obrađeni u petom poglavlju na temelju kojih je donesen zaključak i osvrt na cijeli diplomski rad.

Abstract (english)

The subject of this thesis is the numerical analysis of an ultra-sport car frame. More precisely, the numerical analysis deals with the calculation of the frame torsional rigidity or stiffness. The frame belongs to the Concept One ultra-sport car produced by the car manufacturer Rimac Automobili.

The preface briefly describes the problems engineers have to deal today. Then, the company Rimac Automobili, a leader in development and manufacturing of electric ultra-sport cars, is described. Also a short review of their production range and detailed specifications about the Concept One car are given. The company provided a 3D CAD model of the car frame for the numerical analysis.

A brief history of the development of car frame and desired characteristics are given as a separate chapter within the introduction. The most desired characteristic is the cars rigidity, as a result of frame stiffness. The stiffness is divided in three components, the axial, the flexural and torsional component. Among them, torsional stiffness is a very significant characteristic that shows us whether the car is designed correctly, has less stiffness than desired or required. Also, stiffness is very important for steering and suspension settings because it directly affects the vehicle driveability.

In the third chapter a detailed description of the finite element analysis is given. Finite element analysis is very popular for calculations thanks to available computer technology and was used to make calculations for this thesis. Finite element analysis is integrated in appropriate computer software that uses a lot of hardware resources, such as RAM memory and processor speed. For the analysis one must verify if the available elements are suitable to simulate a real life problem. A verification has been made to ensure that beam and shell elements given in the software ANSYS are suitable to use for analysis of torsional stiffness.

Furthermore, the process of creating the analysis model is described. The first step was to generate the vehicle frame using lines and surfaces in the software CATIA. Next, this frame model was imported in ANSYS software, where tube section properties for each tube and sheet reinforcements thickness were defined. The obtained model was discretized with finite elements, boundary conditions were applied such as torsional moment and displacement suppression. Five meshes (ranging from coarse to very fine) were made and tested to obtain displacement results.

In chapter five the results were evaluated and a conclusion has been drawn.

• Keywords: numerička analiza; simulacija; MKE; torzijska krutost; okvir automobila; šasija; ultra sportski automobili; Concept One
• Keywords (english): numerical analysis; simulation; FEM (finite element methods); torsional stiffness; car frame; chassis; ultra-sport car; Concept One
• Language: croatian
• URN:NBN: urn:nbn:hr:235:331783
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-22 15:33:00