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摘要本文分析了轻型客车的发展概况及发展方向，对轻型客车进行底盘的总体布置设计。
本文参考了国内外十余款同型客车技术参数，并进行参数分析，在任务书的技术参数的要求前提下，进行选择参数，获得更为准确的动力参数。
在计算的基础上对前后悬架和底盘主副车架进行设计，根据我国客车配件市场现状，其余总成部件进行参考选型，在各总成型号参数选定的基础上进行底盘的总体布置设计。
关键词：客车底盘设计动力参数车架钢板弹簧AbstractThis article has analyzed the general situation of M2 cities public transportation passenger train development and direction, generally uses M2 public transportation passenger trains to the major and medium city to carry on the chassis the general arrangement design. In carries on the analysis to the domestic 20 section same types passenger train parameter in the foundation, carries on the parameter choice, and uses mat lab software to carry on the power parameter simulation computation, obtains the more accurate dynamic parameter in order to. Spring and the chassis host & vice frame carries on the design in the simulation foundation to around, other always become the part to carry on the reference shaping, in each always becomes in the foundation which the model parameter designated to carry on the chassis the general arrangement design.key words：Bus Chassis Design Dynamic parameters Frame Spring1.绪论随着世界经济形势逐步优化，我国科技经济文化迅速崛起，尤其是公共交通方面更是位居世界之首。
客车车架结构的优化设计1、选题目的：车架是汽车各总成的安装基体，它将发动机、地盘和车身等总成连成一个有机的整体，即将各总成组成为一辆完整的汽车。
同时，车架还承受各种静载荷和动载荷。
作为汽车重要组成部分的车架则是汽车的“骨骼”，是汽车所有总成零部件“生存”的载体。
车架受力复杂，通过行走系和车身的力都作用于车架上，车架结构的好坏及载荷分配是否合理是汽车设计成功与否的关键之一。
设计合理的车架结构对汽车有着十分重要的意义。
特别对客车底盘，在设计过程中不但要考虑各总成零部件的合理布置以及其方便维修性、可靠性和工艺性，还要充分考虑最大限度地满足车身对底盘的特殊要求，如纵梁的结构、横梁和外支架（牛腿）的位置及连接方式、行李箱大小、地板高度和通道宽度、驾驶区及座椅布置、车门数量和位置等。
对同样型号的客车底盘，不同的用户对车架的要求不尽相同，甚至有较大的差异。
2、研究意义：现代汽车绝大多数都具有作为整车骨架的车架，其功用是支撑链接汽车的各零件部件，并承载来自车内外的各种载荷。
车价是整个汽车的基础，汽车绝大多数不见和总成都是通过车架来固定其未知的。
车架的结构形式首先应满足汽车总体布置要求。
当汽车在复杂的行驶过程中，固定在车架上各总成和部件之间不应该发生干涉，当汽车在崎岖不平的道路上行驶时，车架在载荷作用下可能产生扭转变形及在纵向平面内的弯曲变形，当一边车轮遇到障碍时，还可能使整个车架变成菱形。
因此，车架还应具有足够的强度和适当的刚度，同时还要求其质量尽可能的小，车架应布置的离地面近些等。
因而，如何判断车架结构的合理性及静动态特性的优劣，并对车架结构设计进行优化，是一项十分重要的工作。
客车车架的结构复杂，用经典力学方法不可能得到精确解。
特别是在设计的初期，因无法实测数据，只能依靠经验和类比设计，因而缺乏建立在力学分析基础上的科学依据。
客车车架的设计与制造是开发新车型最重要的组成部分。
由于受各种条件的限制，目前我国基本上还在沿用传统的手工计算方法和连接时的设计与制造过程。
客车车身骨架结构优化设计与先进技术应用发布时间：2021-09-14T06:44:01.537Z 来源：《科学与技术》2021年第14期5月作者：龙宪阁[导读] 随着我国与出行安全相关的法律法规越来越完善，乘用车的整体设计越来越受到重视。
优化车身框架结构设计方案与用料是增加客车的安全性的一种重要方法，龙宪阁辽宁大连 116000 宁波吉利汽车研究开发有限公司摘要：随着我国与出行安全相关的法律法规越来越完善，乘用车的整体设计越来越受到重视。
优化车身框架结构设计方案与用料是增加客车的安全性的一种重要方法，通过合理的设计可以有效的提升客车的安全性。
公交车设计还必须融入更先进的技术，以便公交车设计随着时间的推移而发展并满足现代出行理念的要求。
本文对客车车身设计及先进技术应用进行深入分析，希望对相关人员有所启发，鼓励客车设计的发展。
关键词：客车车身；骨架结构；优化设计；先进技术；应用现阶段，人们越来越重视乘用车的安全性能，能源使用问题也越来越紧张，乘用车的设计过程不仅要注重提高安全性，更要注重采用更先进的技术使乘用车能够运行新的使用能源来减少废气排放总量。
车身框架结构的优化和改进已成为当前汽车制造商的核心研究内容，相关科研机构也在不断加大研究力度。
对这一内容进行深入分析可以帮助广大科研工作者更加清晰的认识车辆的结构特点。
1车身结构机械控制的理论分析客车结构分为非承重、半承重和全承重三种。
全车身结构将成为未来乘用车结构设计的中流砥柱。
非承重或半承重车身与全承重车身最大的区别在于，它有自己的大规格车架，而是用特殊形状的钢管焊接而成的全承重车身，相对较小的横截面总载荷承载结构。
力学分析表明，杆体（薄件）承受轴向变形能力强，抗弯曲性能相对较弱，因此必须保证杆体（框架）具有足够的刚度，一般可以采用增大面积与增加加强筋等方式来祈祷提高强度的作用，通过对局部车架的补强，可以有效提高车辆的整体承载能力的同时不会大幅的增加车辆的自重。
汽车底盘结构的优化在汽车制造领域，底盘结构是一个非常重要的设计要素，它直接关系着汽车的性能、操控和安全性。
为了提升汽车的整体性能，制造商不断进行底盘结构的优化工作。
本文将就汽车底盘结构的优化进行探讨和分析。
一、底盘结构的概述底盘结构是指汽车车体下方的框架和悬挂系统，它承载着车身和引擎，支撑着整个汽车。
底盘结构的主要组成部分包括车架、车轮、悬挂系统等。
优化底盘结构有助于提高汽车的稳定性、减少振动和噪音，并且可以为汽车提供更好的操控性。
二、材料选择的优化在优化汽车底盘结构时，材料选择是至关重要的一步。
汽车底盘需要具备足够的强度和刚度，以承受来自路面的冲击和扭矩。
常见的底盘结构材料有钢铁、铝合金和碳纤维等。
钢铁具有良好的强度和刚度，但重量较重；铝合金比钢铁轻，但强度较低；碳纤维具有极高的强度和刚度，同时重量轻。
优化底盘结构时需要综合考虑这些材料的性能和成本，选择适合的材料来构建底盘结构。
三、悬挂系统的优化悬挂系统对于汽车的行驶稳定性和乘坐舒适性有着至关重要的影响。
优化悬挂系统可以提高汽车的操控性和舒适性。
现代汽车悬挂系统主要包括独立悬挂和非独立悬挂两种形式。
独立悬挂系统具有独立的悬挂装置，可以使车轮独立运动，提高悬挂系统的响应性和稳定性；非独立悬挂系统由其它部件共同支撑车轮，成本较低，但操控性和舒适性略逊于独立悬挂系统。
优化悬挂系统的一种方法是采用可调节悬挂系统，可以根据驾驶条件和需求对悬挂系统进行调节，以提供最佳的悬挂效果。
四、底盘减重的优化底盘的减重对于汽车性能的提升具有重要意义。
减轻底盘重量可以降低燃油消耗，提高加速性能和操控性。
在底盘结构设计中，应该尽量减少不必要的零件和材料，并采用轻量化的设计。
例如，使用轻量化材料代替传统的钢铁材料，采用空心结构代替实心结构等。
此外，通过优化各个零部件的尺寸和形状，也可以实现底盘的减重。
五、结构强度的优化底盘结构的强度对于汽车的安全性和稳定性至关重要。
通过对底盘结构进行强度优化，可以使底盘在承受各种力和冲击时保持稳定，防止车体变形和断裂。
1客车车架总成的结构客车车架按结构型式可分为三种：纵梁式、格栅式及三段式。
纵梁式车架是由贯通前后的纵梁及若干横梁、用铆接或焊接方式连接成的刚性构架。
车架构件一般用低合金钢钢板冲压而成。
格栅式车架(承载底架) 是按整车布置要求设计的空间桁架结构，一般用薄壁矩形管或薄板件焊接而成。
三段式车架由纵梁式和格栅式组合而成，即前后段为纵梁式、中间为格栅式结构。
本文将对纵梁式车架构件的冲压工艺作一些介绍。
2车架纵梁与横梁的冲压工艺客车车架的产量多为中小批量，生产中大多采用一些通用机床、工装、模具，以适应客车多品种、小批量、特殊要求多的特点。
车架构件生产常用冲压工艺有：剪板机剪切下料、冲裁、弯曲、翻边等。
根据车架构件生产的特点，冲压生产中应注意以下几个方面。
2.1剪板机剪切下料根据要求将材料剪切成毛料，下料时应注意排料。
(1) 提高材料利用率。
剪板机下料一般剪为矩形毛料，排样类型为无搭边型。
车架构件生产中合理选择材料规格、合理排样具有很高的经济效益，材料利用率可达90% 以上。
(2) 注意材料纤维方向。
车架构件材料为热轧大梁钢板，板平面方向性比较明显，即材料轧制方向与宽度方向机械性能差别较大，下料时尽量避免后道工序的弯曲线与材料轧制方向相同，应成45°或90°角。
2.2冲裁冲裁是利用冲模使材料分离的一种冲压工艺，包括切断、落料、冲孔、切口等工序。
(1) 冲裁模间隙。
由于车架构件材料厚度厚、硬度高，设计时应尽可能地加大间隙以利于提高冲模的寿命。
冲裁模间隙常采用经验公式：c= m t 来确定，式中：c——单边间隙；t——材料厚度，mm；m ——系数，与材料性能及厚度有关，车架材料一般取8%～12% ，断面质量要求不高时，可以放大到12%～18%。
(2) 冲小孔凸模。
车架构件，特别是车架纵梁上有很多各种规格的安装孔，孔径常为<615～ 30，其中多数为<1015、<1215，大批量生产时可采用冲模一次冲孔、切边，中、小批量则可采用数控冲床逐个冲裁。
基于操纵稳定性的某客车空气悬架系统结构改进本文将针对在客车市场上常见的操纵稳定性问题，探讨一种基于悬挂系统结构改进的解决方案。
目前，很多新车型都采用空气悬挂系统来提高行驶舒适性和稳定性，但仍然存在一些操纵上的问题，例如转向时的后座力和车身倾斜等问题，这可能对驾驶员和乘客安全和舒适造成不良影响。
因此，针对这一问题，本文提出一种新的悬挂系统改进方案，以提高客车的操纵稳定性。
在客车悬挂系统中，空气悬挂被广泛应用。
由于其压力、弹性系数等参数可以随时调整，因此其适应性较强，可以在不同路面和载荷情况下提供相对稳定的悬挂特性。
然而，原有的空气悬挂系统结构并不足以解决客车的操纵稳定性问题。
因此，本文提出了一种新的空气悬挂系统结构改进方案。
这项改进方案主要针对客车侧倾和后座力问题。
在新的悬挂系统中，将采用更多的连接杆和稳定杆等组件，以增加车身的稳定性。
连接杆和稳定杆将分别连接悬挂组件和车身上部结构，以确保悬挂组件的支撑力传递到车身结构中，而不是完全传递到车轮上。
这种连接方式将有效减少侧倾和后座力，从而提高车辆的操纵稳定性。
此外，新的悬挂系统还将配备更多的感应器和控制单元，以实现更精确的悬挂控制和调整。
通过控制单元，驾驶员可以准确地控制悬挂系统的参数，以适应不同路况和驾驶条件。
这将有效改善悬挂系统的响应速度和稳定性。
悬挂系统改进后，还将采用轮边稳定器来进一步提高操纵稳定性表现。
轮边稳定器将分别安装在前后悬挂系统中，以减少车身摇晃和侧倾。
通过调整稳定器的参数，驾驶员可以更好地控制车身的稳定性，以确保在高速行驶或急转弯时获得更好的驾驶体验。
总之，改进空气悬挂系统结构是提高客车操纵稳定性的有效方案。
通过加强悬挂组件和车身连接，采用更精确的控制系统和增加轮边稳定器等组件，可以显著减少侧倾和后座力，获得更平稳和稳定的驾驶体验。
这种技术将在今后的客车制造和设计中发挥重要作用，为驾驶员和乘客提供更高水平的安全和舒适性。
在客车市场中，操纵稳定性一直是一个热门话题，各家车企纷纷为此推出新的技术方案。
客车底盘设计★★★客车底盘设计随着城市化的进程和人们对生活品质的追求，客车作为重要的公共交通工具，越来越受到人们的欢迎和关注。
对于客车来说，底盘是其重要的组成部分，底盘的设计直接影响到客车的性能和安全。
本文将从客车底盘设计的角度进行探讨。
底盘是客车的骨架，主要由梁、轴、弹簧、减震器、制动器、转向机构和驱动系统组成。
底盘的设计目的是使得客车具备足够的承载能力和稳定性，在道路上行驶时保证乘客的安全和舒适性，并且满足城市道路的通行要求。
客车底盘设计的要点有以下几个方面：1. 承载能力和稳定性客车是大型车辆，其载荷量和重心高度都较高，因此底盘的承载能力和稳定性显得尤为重要。
底盘的结构应具备稳定性，不能出现扭曲、变形等现象，同时要考虑客车行驶时的颠簸和冲击，必须严格控制底盘的弯曲和位移。
2. 舒适性和噪音控制客车底盘的结构和悬挂系统，对乘客的舒适性有很大影响。
底盘的弹簧和减震器的刚度和质量应该符合设计要求，以减少车辆颠簸和震动，并且降低车内的噪音。
此外，轮胎型号和胎面结构也对车辆的舒适性和噪音控制产生重要影响。
3. 制动性能客车的制动系统必须具备良好的制动性能，才能保障车辆在急刹车或紧急情况下的安全。
底盘的制动器与轮胎、制动片、刹车鼓等配件配合良好，才能保证客车制动性能的稳定和可靠性。
4. 匹配车身结构底盘与车身结构之间的匹配是客车设计的重要环节。
车身与底盘的配合性应该良好，使得车身和底盘的整个结构具备合理的协调性，在行驶时能更好的支撑和保障车身的稳定性。
5. 节能环保节能环保是现代客车底盘设计的重要理念。
底盘的设计应该具备优异的动力学性能和燃油经济性，以降低燃油消耗和减少排放，达到节能环保的目标。
客车底盘设计是一个包罗万象的工程，需要从多个角度进行综合考虑和优化。
只有在底盘设计过程中充分考虑以上要点，才能设计出性能和安全都良好的客车底盘，为人们的出行带来更多的便利和舒适。
客车车架减重分析优化作者：石磊戈宏伟罗辑来源：《时代汽车》2021年第16期摘要：車架作为车辆的主要支撑部分，对车辆的使用性能以及乘客的舒适性有着极大的影响。
本文主要是通过对客车常见的三段式车架进行有限元分析，建立了一个三维模型，主要是分析了三段式车架在弯曲和扭转条件下的位移应力分布及其位移关系。
通过分析，找到应力最大点和位移最大点，对其周围结构和零件进行分析。
发现其应力过大和位移较大的原因是零件的形状设计不合理，以及结构的不合理。
通过将零件的截面由原来的槽钢改变为具有桁架结构的零件，这样，不仅减小了车架的重量，还优化了零件的性能。
对于车身结构，主要优化为在行李架处添加一个支撑件。
通过以上两个改进，降低了车身的最大应力以及最大位移量。
对车架结构的性能已经乘客的乘坐舒适性都有极大的改善。
关键词：车架减重优化Analysis and Optimization of Weight Loss of Passenger Car FrameShi Lei Ge Hongwei Luo JiAbstract：As the main support part of the vehicle， the frame has a great impact on the performance of the vehicle and the comfort of passengers. In this paper， through the finite element analysis of the common three-segment frame of passenger cars， a three-dimensional model is established， which mainly analyzes the displacement stress distribution and the displacement relationship of the three-segment frame under bending and torsion conditions. Through analysis， the article finds the maximum stress point and the maximum displacement point， and analyzes the surrounding structure and parts. It is found that the reason for the excessive stress and large displacement is the unreasonable shape design of the parts and the unreasonable structure. Changing the section of the part from the original channel steel to a part with a truss structure， not only reduces the weight of the frame， but also optimizes the performance of the part. For the body structure， the main optimization is to add a support at the luggage rack. Through the above two improvements， the maximum stress and maximum displacement of the car body are reduced. The performance of the frame structure has greatly improved the ride comfort of passengers.Key words：frame， weight reduction， optimization1前言车架是车的主要载体。
运用CAE技术进行某微型客车车架结构的分析与优化设计苏庆1 孙凌玉1 刘福保2（1.北京航空航天大学汽车工程系北京 100083）（2.江西昌河汽车股份有限公司合肥分公司合肥 230000）摘要：本文运用几种CAE技术对某微型客车车架进行了结构分析与优化设计，首先，计算了静力挠度，静态弯曲、扭转刚度，然后求解了固有模态，并在此基础上获得典型道路激励下的瞬态响应，此外，还对车架典型薄壁梁结构的耐撞性吸能特性进行研究，配合实验数据，对车架结构进行了合理的改进设计，实现了满足轻量化要求的静态优化设计目标，彰显CAE技术在汽车研发过程中的作用日益重要。
关键词：CAE，车架，优化设计0综述CAE（计算机辅助工程分析）技术的兴起及应用，滞后于CAD（计算机辅助设计）技术，尤其在汽车工业以及机械行业。
当前，在中国汽车行业CAD技术已广泛得到应用，在产品设计过程中已经摈弃手工绘图的时代，将企业中的图纸信息数字化，大大节省成本；而对于产品进入验证阶段所必需的试验，对所设计的产品进行符合国家相关法规标准的强度、刚度、NVH、耐撞性等方面的评价，企业必须对概念样品进行一次一次的试验、修改、再试验、再修改的反复过程，最后才可以定型，生产销售。
相对于在产品设计初期的方案拟定、图纸绘制工作所耗费的人力、物力、财力，在设计进入验证阶段的反复试验评价和改进样品的费用可谓是天壤之别。
然而，CAE技术已在国外大型汽车企业中广泛应用，用以降低成本，缩短新车开发周期，应对瞬息万变的汽车市场需求，我国大部分汽车企业也都接触到CAE的研发工具，但应用的能力还不强，真正应用到产品研发中的企业还是很少，运用CAE软件进行分析的能力决定所开发产品的水平。
本文结合某微型客车车架结构，对其进行轻量化以及耐撞性能优化设计，效果良好，得到厂家的肯定与应用。
各工况分析的模型采用基于该微型客车CAD模型的有限元模型，减少建模的误差，进行分析。
该车架的有限元模型如图1所示。
SAE TECHNICAL 2002-01-3383PAPER SERIES EFrame Structure Optimization for Bus ChassisFlavio Henrique Vieira de AguiarDaimlerChrysler do BrasilDaniel Muller SpinelliDaimlerChrysler do BrasilAlexandre PazianDaimlerChrysler do BrasilMarcos Carazatto GimenezDaimlerChrysler do BrasilAll rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.For permission and licensing requests contact:SAE Permissions400 Commonwealth DriveWarrendale, PA 15096-0001-USAEmail: permissions@Fax: 724-772-4891Tel: 724-772-4028For multiple print copies contact:SAE Customer ServiceTel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724-776-1615Email: CustomerService@ISBN 0-7680-1109-4Copyright © 2002 SAE InternationalPositions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the paper if it is published in SAE Transactions.Persons wishing to submit papers to be considered for presentation or publication by SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USA2002-01-3383Frame Structure Optimization for Bus ChassisFlávio Henrique V. de AguiarMarcos Carazatto GimenezAlexandre PazianDaniel Muller SpinelliDaimlerChrysler Brazil Ltda. Copyright © 2002 Society of Automotive Engineers, IncABSTRACTThis paper describes the methodology used at DaimlerChrysler Brazil Ltda. (DCBR) for bus chassis frame structure optimization resulting from constant product improvements. The objectives were the reduction of weight and costs for the frame components.At first, a research about frame structure components current situation was done considering the features, investments, and previous finite element analysis.Then the modifications were evaluated through static and dynamic numeric simulation analysis. In the end of third analysis step, the results were approved releasing the geometry for a physical prototype construction, that was monitored during the durability test to confirm the weight and cost reduction of about 15% of frame current structure.After the durability test accomplishment all approved modifications were released for production. INTRODUCTIONDuring a bus chassis frame structure development process a weight reduction study was requested in order to improve the product requirements, as the bus world market demands a vehicle which, besides the technical innovations, can compete having a lightweight construction. This vehicle will be enabled to carry more passengers and luggage, respecting the maximum axles loads legislation.VEHICLEThe frame structure has been developed for two different kinds of chassis, City bus and Intercity bus, which has theirs components unified to share the investments of production among the new product range. The chassis has a modular concept that allows flexibility to compose thisproduct range, as shown on Figure 1 and 2.Figure 1: City bus frame2 axles3 axlesFigure 2: Intercity bus or Coach frame OBJECTIVES• The main objective of this work is to reduce the weight of the frame structure.• A second goal is to reduce the cost without compromising the quality and reliability of the product. • The last but not the least, to improve the production processes through of modification the some parts. METHODOLOGYAt first a benchmarking was done to verify the competitors weight performance and to establish a goal. Then a research to know the current situation considering weight, material quality, die tools and fixture investments, and previous finite element analysis was done.In the optimization was considered mainlythickness reductions, avoiding part shape changes for saving the investments that have already been done. However a material weight reduction brings a cost reduction as the steel is bought in tons.Analyzing the previous Finite Elements Analysis(FEA) results, it could be observed the components with more potential for thickness reduction. A table with all modification proposals according to optimization criteria was created as checklist.Considering these modification proposals the newFEA for chassis evaluations was done. The FEA activities were conducted by T-Systems , which applies the calculations procedure and criteria adopted by DaimlerChrysler Germany (DCAG). This analysis takes into account the identification of possible stress concentrators.At the end of the first analysis loop a design reviewteam, which had representatives from design, manufacturing, quality control, advanced planning and purchasing verified the detail drawings and the first FEA results. Figure 3 shows a cast part before and after firstoptimization.20 kg27 kgFigure 3: The cast part before and after optimization After the last loop analysis, accomplished withsuccess, the geometries were frozen considering that the shape of parts had a very good maturity level for a physical prototype construction. Figure 4 shows an optimized chassisprototype, which was sent to durability test.Figure 4: The chassis prototype optimizedThe durability test was done following twosimultaneous tracks, one was done in Stuttgart (Germany) on the “Rough-track” Road and the other in Indaiatuba (Brazil) on the “Off-road-track”.Having the optimized parts approved in thedurability tests, engineering started the process of releasing, detailing the geometries with CAD and preparing the documentation, which all the company will access, for mass production.FINITE ELEMENTS ANALYSISThe objective of the analysis through FiniteElements is to detect stress concentrated regions and guide correction actions followed by possible new optimization proposals.In this work static and dynamic criteria wereapplied so as to comprehend entire application of the vehicle. These criteria are related to mechanical properties of used materials. For static calculations, the stress must be below the allowable static limits. For dynamic calculations, the stress must be below the allowable fatigue limits. For the evaluation of the optimized chassis, staticanalysis for weight, lateral acceleration, symmetric and asymmetric breaking, torsion, and engine first gear torque, as well as dynamic analysis, on which the model was submitted a “Rough-track” signal were conducted, as shownon Figure 5.Figure 5: Finite element result for static analysisIn the first calculation loop many stress points which exceeded allowable limits were detected. To illustrate the proposal validation process three points around the frame structure were selected.Point 1, Module 2 – symmetric breaking – 125%of allowable stress, as shown on Figure 6.Figure 6: Point 1Point 2, Module 4 – dynamic analysis – 145% ofallowable stress, as shown on Figure 7.Figure 7: Point 2Point 3, Module 5 – dynamic analysis – 149% ofallowable stress, as shown on Figure 8.Figure 8: Point 3In the second loop calculation the above points were reworked. Having the following results:Point 1 – The tube thickness was analyzed with 6,3 mm instead of 4,75 mm to and the welding from 5 mm to 7 mm. The stress was reduced from 125% to 98%.Point 2 – The welding turned to be continuous in the whole profile contour and a bracket was added, as shown onFigure 9. The stress was reduced from 145% to 100%.Figure 9: Point 2Point 3 – The materials thickness was analyzed with 8mm instead of 6 mm. The stress was reduced from 149% to 98%.All points that exceed in 10% the allowable limits will be monitored during the durability tests and evaluated as for safety.There were some restrictions related to dimensions, materials and thickness standardization. In this way, it was not possible to implement all of the proposals that contributed to stress reduction on the structure.In some situations that restrictions turned the optimization impossible the durability tests stress measurements data from same family vehicles were used as comparison.For instance, in point 1, the thickness 6,3 mm wasnot implemented, keeping 4,75 mm as in the same family,the same region, the ratio along stress measure in durabilitytests and others from calculations, gave a safety margin of74%. This means that forces in some regions were considered too conservative. Points with characteristics likethat were kept as observation points.TESTRisks are inherent in anything new. Thereforedurability tests are done for checking the optimized components on tracks with different profiles due to timeresponse needs. Table I presents the test period for accomplishment. One is a “Rough-track” and the other is a“Off-road-track”, as shown on Figures 10 and 11.Table I: Tracks FeaturesRough-trackUnpavement-track Length (km) 1,7 17Km per day 100 150Sign-off (km) 5,000 30,000Period (day) 50 200Figure 10: The City bus in the “Rough-track”Figure 11: The Intercity bus or Coach in the “Unpavement-track”Analyzing the calculation results, it could beobserved that the vehicles should be monitored during thedurability tests. On regions with stresses close or 10% higher than were considered acceptable limits.For keeping control of these critical points, some strain gauges were fitted on the structure parts to figure out the actual strains during the durability program, as shownFigure 12: Critical points measurementWhen the results of calculation were compared to the measured values, it was realized that the improvements had been done with safety.In order to go ahead, the optimized parts releasing times for other areas, in order to fulfil production process new requirements, was done simultaneous to the testing program by engineering through risks evaluation. But the vehicle will be launched only when the durability tests are finished, respecting the maturity level criteria.DETAILING DESIGNAs stated in the introduction, all the process started preparing parts drafts and assemblies to the prototype construction, as shown on Figure 14, intending to feed all the involved areas. After this, design releasing (project/documentation) was started. Firstly the schedule was made to determine the time limit so as to share all theactivities among the staff.Figure 14 - The frame structure optimizedPROJECT RELEASEAll parts were analyzed in order to develop them interchangeable, so new parts were created only if interchangeability was not possible. After verifying all the pros and cons of the 3D geometries, they were modified or new ones created, changing thickness, material specification and in some cases also shapes.Basically the detailing design is divided in two parts: drawings and 3D geometries. So, one assembly can have many space models which were assembled in a Geometry Information System (GIS). The assemblies and drawings were built and updated with the new 3D models.Figure 15 shows the software used to detailing design.Figure 15 – CATIA 3D and 2D screen grabDOCUMENTATION RELEASEThe application of all parts for the whole vehicle family are released in this step and saved in another databases the Development Documentation System (EDS/BCS). At this stage, the project was released with a provisory maturity level at which the factory still cannot start the productive process modification. This maturity level will be changed only after the approval of the durability tests. And lastly, the Product Documentation System (PDS) that has the interface with the line assemblyis updated. Figure 16 shows the software used todocumentation releasing.Figure 16 – GIS and EDS/PDS screen grabAfter these activities were done, all DaimlerChrysler’s branches can read these drawings,geometries, and documentation around the world, so any DaimlerChrysler division can manufacture the components. CONCLUSIONAs a conclusion, it can be started that this workaccomplished the initial targets as following:1) This Table II below presents the weightreduction results.Table II: Weight reductionFrame structureIntercityWeight(kg)City2 axle3 axleCurrent 1395 1206 1279 Optimized 1096 935 993 Reduction 301271286% 21,58 22,47 22,242) This Table III below presents the cost reduction results.Table III: Cost ReductionFrame StructureIntercityCity2 axle3 axleCost Reduction (%) 15 20 183) The work together with production improved the design for assembly and manufacture by changing geometries concept and material specification.As resume, the optimization results inserted the vehicles in good market position regarding weight and price.ACKNOWLEDGEMENTSThe authors would like to thank DaimlerChryslerBrazil L tda, with special mentions to Mr. Sergio Simões, Manager of Bus Chassis Technology, for the opportunity to develop this work. REFERENCESSpinelli, D, Modular Bus Chassis DevelopmentUsing Modern Simultaneous Engineering Tools, 2001. T-Systems, Calculation for chassis of road bus IBC2036 and CBC 1725 – Structural optimization, 2001/2002.T he appearance of the ISSN code at the bottom of this page indicates SAE’s consent that copies of the paper may be made for personal or internal use of specific clients. This consent is given on the condition however, that the copier pay a $ 7.00 per article copy fee through the Copyright Clearance Center, Inc. Operations Center, 222 Rosewood Drive, Danvers, MA 01923 for copying beyond that permitted by Sections 107 or 108 of U.S. Copyright Law. T his consent does not extend to other kinds of copying such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale.SAE routinely stocks printed papers for a period of three years following date of publication. 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For permission to publish this paper in full or in part, contact the SAE Publications Group.Persons wishing to submit papers to be considered for presentation or publication through SAE should send the manuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE.。
