Reading, Research and References (CZ)

Wednesday 26th August, 2020.

Impact test of a crash-energy management passenger rail car.

In this study the chassis showed improvements in its crashworthiness. This deduction was made since the passenger compartment remained unaffected during and after the crush.

Reference:  https://ieeexplore.ieee.org/abstract/document/1300895 

Cars are designed to crumple.

This YouTube video from the Age & Sydney Morning Herald summarizes the concept of crumple zones.  The front and rear end of vehicles are designed to absorb the energy during a crash to protect the passengers. The vehicle deforms in certain parts so that other parts of the vehicle remain in tact to protect the passengers. Certain creases and grooves are placed to allow the part to crumple in a controlled manner, other components are added to prevent parts from crumpling for example: hooks that prevent the bonnet from crumpling into the windscreen. When impacted from the side, most vehicles have the central pillar made of stronger metals at the top and softer metals at the bottom so that the energy is absorbed and is passed under the passenger and protects the head and torso. There are various metals used in the frame to serve different purposes. So the frame should maintain its shape and divert the crash away from the passengers inside. 

Reference:  https://www.youtube.com/watch?v=kly5BM8G3iM 

Volkswagen Car Safety

Volkswagen discussed the crumple zones used in their vehicles to protect their travelers. For this project consider roll-over bar system and foot protection. In the roll-over system the windscreen frame is reinforced for extra protection. 

Reference:  https://www.volkswagen.co.uk/technology/car-safety/crumple-zones 

 Friday 28th August, 2020
Automotive Chassis Engineering Notes (David c. Barton, John D. Fieldhouse).
Chapter 4: Vehicle Structures and Materials
4.1 Review of Vehicle Structures
"Consider different materials used in vehicle structures with a focus on reducing vehicle weight and therefore emissions through the use of high strength steel, aluminum and composite materials."
Ladder frames would have the body shell attached to them and its min purpose was to protect against elements. The mountings were flexible thus the vehicle had little stiffness.
This structure is heave and has a high section modulus. The difference in stiffness between the frame nd the body shell causes mounting problems.
Integral/unitary structures is such that the whole body is an integral unit. It can carry the applied loads while possessing the stiffness the vehicle requires.
3D form in the manner it deforms and carries load while resisting bending and torsional loads. Manufactured from thin sheet metals. Required to be stiffened with reinforcements.


Tuesday 01st September, 2020
The Automotive Chassis Vol.1: Components Design (Giancarlo Genta,  Lorenzo Morello)
1 Wheels, Structures and Mechanisms
Historical Evolution
1.6 Chassis frame

Car body manufactures/ automotive industry

There were two groups the chassis manufacturers as well as the body manufactures. The chassis manufactures focused on building the vehicle of metallic materials despite it being more difficult to shape and paint than wood. Body manufactures developed wooden structures and wood was favored more for obtaining curved shapes and painting. The chassis and the boy is separated during manufacturing to prevent damaging mechanical parts. The chassis manufacturer would deliver the chassis to the body manufacturer to be completed for sale. Eventually, the chassis and the body were integrated where the chassis would carry the load of the components as well as the body. The early frame design is known as the Ladder-Frame structure comprised of two longitudinal rails with cross members to resemble a ladder. This frame allowed space for the axles and the engine to be mounted. This structure is still used for industrial vehicles. Sheet steel body panels became favourable for the increase in flexibility, however, it also increased the overall stress of the structure? 

It is important to note that the chassis no longer exists as a physical subassembly of mechanical components... (review undnerlined statement)

Wednesday 09th September, 2020
The Automotive Chassis Vol.1: Components Design (Giancarlo Genta,  Lorenzo Morello)
7 Chassis Structures
These structures experience both internal and external loads. The internal loads are due to the mass of the vehicle, payloads as well as reaction forces from the power train suspension. The external loads however, originate from the contact between the vehicle wheels and the ground and aerodynamic fields. Chassis structures may be separated from the body or integrated (e.g. unitized bodies). As such the structures exist in three categories, frames, underbodies and subframes.
7.3 Industrial vehicle frames

Industrial vehicles uses the ladder-frame structure. This frame lends its stiffness to carrying significant loads therefore, the torsional stiffness of the frame should be great and this depends on the rigidity of the cross members in the ladder frame. (if additional information is needed see the document.)
7.1 UnderbodyA unitized body cannot by disassembled after it is made and it bears all the vehicle loads directly. The parts of the body that does not have limited structural function is referred to as the body shell. Those parts without a structural function include removable parts such as the doors, glass and the interior of the vehicle. The windshield adds to the body stiffness when it is bonded to the body. The shape of the cross beams found in the shell determine the effectiveness of the body's ability to resist deformation in certain area, absorb energy and protect the occupants in case of mischance. " The underbody has a functional analogy to the chassis of an old car or industrial vehicle. "The pair of longitudinal side beams are connected to the cross beams through welds. The floor panel is attached to these longitudinal beams. (Consider the additional information in this chapter when designing the improved chassis.)
7.2 Subframe

These are also known as auxiliary frames. They serve the following functions when attached to a unitized body structure:(taken directly form document) • They offer suspensions and power train mounts and distribute the consequent loads to the body area most suitable from a structural standpoint. • They built up a secondary suspension, when mounted on the body with elastic elements, able to filter vibrations from the powertrain and wheels, at frequencies critical to acoustic comfort. • They contribute to managing body deformations in the event of a crash. • They offer an assembly support to many elements of the chassis, with benefits for work organization. • Their reduced dimensions, as compared with the dimensions of the body, allow better control of tolerance of the suspension mounts, with benefits for their elasto-kinematic behavior.
The chassis components are assembled on the subframe and the subframe is attached to the body by two large mounts. It is made of a pair of stamped steel shells spot welded along a mounting flange. An alternative for this structure is using an aluminum casting. The subframes used in small and medium cars differ. (Consider the additional information in this chapter when designing the improved chassis.)

Friday 11th September, 2020
The Automotive Chassis Vol.1: Components Design (Giancarlo Genta,  Lorenzo Morello) 7.4 Structural tasks

• bear forces
• bear payloads
• resist deformation

7.4.1 External loads
External loads may be instantaneous overloads or fatigue loads. Instantaneous loads are considered as static loads and can occur when driving over pits, hitting curbs or even sudden braking. A vehicle may experience fatigue loads when driving a long bumpy roads. Driving loads  are a result of vehicular manoeuvers. They are transferred to the chassis through the suspension and are considered as static loads. These forces are present when steering or applying brake. There are loads due to uneven ground that causes the vehicle subsystems to rect dynamically.
7.4.2 Internal loads
Some internals loads come from the internal combustion engine due to reciprocating masses.

Friday 28th August, 2020

Automotive Chassis Engineering Notes (David c. Barton, John D. Fieldhouse).

Chapter 4: Vehicle Structures and Materials

4.4 Safety Under Impact

4.4.1 Legislation

Active and Passive safety.

"Secondary safety is concerned with minimising the risk of injury to the vehicle occupant and other road users in the event that an accident should occur."

4.4.2 Overview of Frontal Impact

"In the frontal impact of a vehicle whether with a barrier or another vehicle, the worst case scenario is that all the initial kinetic energy of the vehicle on impact is dissipated within the structure of that vehicle alone."

4.4.3 Energy Absorbing Devices and Crash Protection

"The front bumper of a passenger car is normally the first component to be impacted in a frontal collision. Bumper design has evolved from a simple steel construction designed to protect the bodywork from small knocks towards the complex polymer/foam/metal construction of modern bumper systems ."

4.4.4 Case Study: Crashworthiness of Small Space frame Sports Car

Unlike the study conducted in this project, this document focuses on a space car. In collision the front wheel s come in contact with the barrier before any other part of the vehicle in a frontal impact. Therefore there is limited usefulness in this section wrt to the project conducted.

Thursday 10th September, 2020

The Automotive Chassis Vol.1: Components Design (Giancarlo Genta,  Lorenzo Morello) 

7.6 Structural Testing

" The most important test, specific to chassis structure and the body shell, is the overall evaluation of torsional stiffness."

Local deformations due to bending and torsion are identified further, these deformation discontinuities give insight to rupture points that may occur while the vehicle is in use due to road obstacles.

Friday 28th August, 2020

Automotive Chassis Engineering Notes (David c. Barton, John D. Fieldhouse).

Chapter 4: Vehicle Structures and Materials

4.2 Materials for Light Weight Car Body Structures.

Reducing the mass of the vehicle also reduces the amount of fuel the vehicle uses. Additionally the vehicle's acceleration and deceleration performance. 

AHSS are now being used to enhance mechanical properties due to how well it absorbs energy upon impact. Some examples of AHSS are phases of hard steel containing martensite, bainite or austenite.

"The resulting enhanced yield stress enables panel thicknesses to be further reduce but also causes manufacturing difficulties due to the reduced ductility and the high amounts of elastic energy stored that can exacerbate problems such as spring-back."

Forming difficulties are countered using tailor-welded blanks (TWB).  This method enhances formability by increasing thickness in certain areas for structural stiffness and decreasing thickness in other areas. Consequently weight is reduced.

High end passenger cars are now being made with more aluminum allows for he body shells because of its lower density in comparison to steel. Metallic material with high yield strength tend to have lower ductility so its harder to form shells with them. As a result advance body shells uses pressed sheets and extruded and cast aluminum components.

Aluminum is difficult to recycle. 

Composites cannot be welded adhesive joining is used.

Cheap, Lightweight, Stiff and Strong.