Automotive Bumper Materials

Topics: Steel, Welding, Tensile strength Pages: 19 (5045 words) Published: September 29, 2013
Steel grades for reinforcing beams and typical properties [9]
Notes:

HR - Hot rolled sheet

CR - Cold rolled sheet

HDG (CR) - Hot-dip galvanized (cold rolled base) sheet

EG (CR) - Electrogalvanized (cold rolled base) sheet

SS - Stainless steel

XLF - Microalloy quality. Strength is obtained through small quantities of alloying elements such as vanadium and niobium. Designation number (e.g. 50) is mimimum yield strength in ksi.

..B..(M) - Carbon-boron quality (Modified). Properties are for the steel as-shipped from the steel mill. Strength is achieved through heating and quenching. After quenching, the yiel strength is about 1140 MPa (165ksi)

..B.. - Carbon-boron quality. Properties are for the steel as-shipped from the steel mill. Strength is achieved through heating and quenching. After quenching, the yield strength is about 1140 MPa (165ksi)

XF - Recovery annealed quality. Strength is achieved primarily through cold work during cold rolling at the steel mill. Designation number (e.g. 120) is minimum yield strength in ksi.

M...HT - Martensitic quality. Strength is determined by carbon content. 140T - Dual phase quality. Structure contains martensite in ferrite matrix. Properties are for the steel as-shipped from the steel mill. Designation number (e.g. 140) is the minimum tensile strength in ksi.

1. Abstract
A detailed study on materials used for automotive bumper beams has been carried out with the key objectives of identifying the key property requirements, the currently used materials and alternative candidate materials. This report presents a detailed analysis of their respective advantages, drawbacks and a comparative ranking of these materials. The best alternative material has then been identified and a suitable manufacturing process for the bumper beam (using the best alternative material) has been described.

2.Introduction
Front and rear bumpers became standard equipment on all cars in 1925 [17]. What were then simple metal beams attached to the front and rear of a car have evolved into complex, engineered components that are integral to the protection of the vehicle in low-speed collisions. Today's auto bumpers and fascia systems are aesthetically pleasing, while offering advantages to both designers and drivers. Until 1990s, virtually all structural bumper beams were steel or aluminium. The exposed steel beams were decorated by painting, chrome plating or covering with cast polyurethane. Then plastics took over this market because of the need for weight reduction and corrosion resistance. Distinctive styling is a fast growing theme today. This trend is characterized by the giving attractive and distinct shapes to the turn signal lamps, air flow grills, and other trim pieces in the bumper system area. Lighter, more efficient front ends are required with improved performance to match the fuel efficiency and safety requirements of today. Bumper systems are integral parts of the overall automotive business goals of increased perceived quality, distinctive styling, and increased number of niche products.

Metal facebar

Plastic fascia and reinforcing beam *

Plastic fascia, reinforcing beam * and mechanical energy absorbers

Plastic fascia, reinforcing beam* and foam or honeycomb energy absorber

* Reinforcing beam refers to the bumper beam here
Fig1. Common Bumper Systems[9]

2.1 Bumper System – Description:
Typically a modern bumper system consists of
An outer bumper surface (appearance face) which can either be a rigid beam or a flexible fascia •A structural bumper beam(or reinforcement), which can either be a separate component or part of the face bar assembly •Mounting brackets to attach the bumper beam to the vehicle structure, which can be rigid, returnable or crushable (partially non-returnable) If the mounting brackets are rigid, there normally is a crushable energy absorbing...
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