Thursday, 27 November 2014

Material composition in a vehicle


MATERIAL selections have been the primary exercise in the design and development of automotive vehicles since the early days of mass production.
The general trend showed that the material development and innovations were focused on weight reduction of the vehicles with the introduction of materials which were inexpensive and yet superior in mechanical properties.
Car users are more familiar with the functionality of their vehicles such as the engine, transmission and ABS system, but little thought is given to the raw materials that are used in the production of the vehicles.
Automotive manufacturers use a tremendous number of materials in the mass production of their vehicles.
The types of materials vary from the smallest parts such as screws and clips to the larger components such as engine and transmission. Five major materials are predominant in the development of a vehicle and their utilization has significant impact on the weight and cost of the vehicle produced.
Steel was largely used by automobiles of the late 1980s for the body and frame, to produce vehicles that were strong but heavy. The vehicles compromised on fuel consumption as they had lesser value compared with the vehicles today.
Percentage composition by weight of the major materials include high strength steel about six per cent, other steel 50 per cent, iron 15 per cent, plastics seven per cent, aluminium four per cent and others (such as rubber, glass, textile) about 18 per cent.
Aluminium began to replace steel and iron components in the mid 1990s, thereby reducing the weight of the vehicle, leading to significant improvement in the performance.
Composition of major materials during this period was altered as following: high strength steel 10 per cent, other steel 43 per cent, iron 12 per cent, plastics seven per cent, aluminium eight per cent and others about 20 per cent.
Attempt to reduce the weight and cost of modern cars in the late 2000 had led to the use of more plastic materials and reduction in iron-made components. The composition of major materials was then: high strength steel 13 per cent, other steel 42 per cent, iron seven per cent, plastics nine per cent, aluminium eight per cent and others 21 per cent.
The weight of a modern vehicle is centered on the body, including frame and panels that are attached to it. According to current estimation, the body constitutes 40 per cent of the vehicle weight.
Interior components contribute some 15 per cent, while chassis and power train make up 24 per cent and 16 per cent of the vehicle weight, respectively.
However, the percentage may differ in vehicles that use sub-frames for front-wheel drive instead of chassis, which is more common for rear-wheel drive. Electrical systems are more in use in modern vehicles as technology advances further, contributing to five per cent of the vehicle weight.
It is apparent that for further weight reduction exercises, more focus should be given to body design and construction using lighter materials than high strength steel. Composite material is becoming the best available choice for vehicle body. Metal and ceramic composites may offer alternatives in replacing some of the iron and other steel parts.

Wednesday, 19 November 2014

Heat treatment of metals ensures quality car parts


MECHANICAL properties of many metallic materials can be manipulated by the process called “heat treatment”, a phenomenon practiced since antiquity. The practice now is an advanced science in any manufacturing of metallic components.
Steel and aluminium alloys are among the most popular heat-treatable materials that are widely used in the manufacture of automotive parts to achieve the desired properties.
Heat-treatment produces a great variety of micro structural changes or transformation within the metal matrices during heating and cooling in their solid states. The right transformation that occurs in the final micro structure will result in the component having the mechanical properties required to serve its function.
Steel is an alloy of iron and carbon with iron being the base metal. Heat-treatment procedures transform the iron-carbon compound in the steel matrices into a variety of steel micro structures. These transformations result in the variation of the properties of steel, such as; tensile strength, hardness, toughness, ductility etc.
Heat-treatment processes such as annealing, hardening, normalizing and tempering are familiar among metallurgists and engineers in manipulating the properties of steel at various levels of processes and finishing work in components manufacturing.
On a similar account aluminium alloy with silicon is the most popular lightweight material that is heat-treatable. The alloy, in the presence of a right quantity of silicon and magnesium, transforms into aluminium-silicon-magnesium compound in the micro structure of the alloy after heat-treatment. The procedures strengthen the alloy as well as improve its properties amongst which are; ductility, tensile strength, impact strength and fracture resistance.
The quality of tools (moulds and dies) for mass production of components as described in the previous article, demand right heat-treatment procedures to ensure longer operational lives.
This article does not intend to elaborate in depth on the scientific and metallurgical aspects of heat-treatment of metals, but suffice to demonstrate the importance of heat-treatment of in achieving the required properties of metals used in any engineering endeavour and in the manufacture of quality parts and components.
There are 20 local heat-treatment companies that provide heat-treatment services, such as; vacuum hardening, carburising, carbonitriding, nitriding, annealing and tempering, to the local automotive industries.
Heat-treatment facilities are best installed within the production line of a mass component manufacturing set-up. This is to ensure that operation flows are without interruptions. Sub-contracting heat-treatment work to another party may render inefficiency in the production line process sequence.
There seems to be sufficient metallurgical and practical knowledge on heat-treatment processes amongst the downstream steel industries due to their long term establishments.
However, knowledge on metallurgical aspects and heat-treatment procedures for aluminium alloys seems inadequate within the local aluminium parts manufacturers. Some of the producers heat-treat their manufactured parts without in-depth knowledge on the microstructural transform that occurs during the process.
Enhancing the heat-treatment knowledge and capabilities amongst the aluminium industrialist is crucial as the nation embarks on the manufacture of energy efficient vehicles.
Aluminium as a lightweight material is expected to be extensively used in these vehicles.