Hydroforming Techniques

Definition

The hydroforming technology has gained in importance over the last few years. Today the lightweight construction of automobiles is one of the main fields of application. This paper gives an overview of the fundamental principles of hydroforming processes and their variants. The correlations between the work piece geometry and the design of tool and process and the forming result are exemplarily illustrated. Hydroforming is a cost-effective way of shaping malleable metals such as aluminum into lightweight, structurally stiff and strong pieces. One of the largest applications of hydroforming is the automotive industry, which makes use of the complex shapes possible by hydroforming to produce stronger, lighter, and more rigid unibody structures for vehicles. This technique is particularly popular with the high-end sports car industry and is also frequently employed in the shaping of aluminum tubes for bicycle frames.

Hydroforming is a specialized type of die forming that uses a high pressure hydraulic fluid to press room temperature working material into a die. To hydroform aluminum into a vehicle's frame rail, a hollow tube of aluminum is placed inside a negative mold that has the shape of the desired end result. High pressure hydraulic pistons then inject a fluid at very high pressure inside the aluminum which causes it to expand until it matches the mold. The hydroformed aluminum is then removed from the mold.

Hydro forming is a relatively new process, which uses water pressure to form complex shapes from sheet or tube material. Design studies suggest that automobiles can be made much lighter by using hydro formed components made of steel. Structural strength and stiffness can be improved and the tooling costs reduced because several components can be consolidated into one hydro formed part.

As the automobile industry strives to make car lighter, stronger and more fuel efficient, it will continue to drive hydro forming applications. Some automobile parts such as structural chassis, instrument panel beam, engine cradles and radiator closures are becoming standard hydro formed parts.

The capability of hydro forming can be more fully used to create complicated parts. Using a single hydro formed item to replace several individual parts eliminate welding, holes, punching etc... Hydro forming simplifies assembly and reduce inventory.

Tube Hydro Forming:

Tube hydro forming is a kind of soft-tool forming technology and developed rapidly in the past decades. For taking tubes as processing blanks and liquid as flexible punch, it is more suitable for manufacturing special tubular components, such as different kinds of hollow shafts, discharge pipe of automobile & aero planes, sectional pipes etc..

Tubes were placed in the die and sealed on the end. Then under the co-action of compressive axial force and internal pressure, it is forced to deform from elastic stage to plastic stage. With the increasing of the applied load, the deformation increased correspondingly. Finally, under the extremely high pressure, the tube assumed the internal contour of the die precisely. In tube hydro forming, a cylinder is pressurized internally with 80 to 450 MPa pressure by a fluid like water.

Compared with traditional processing technology, tube hydro forming always manufactures components at one step. So it can enhance part quality, such as tighter tolerance and increase rigidity, and lower production costs and reduction in production cycle. In this method the tube is placed in die and as press clamps the die. Valves, low pressure fluid is introduced into tube to pre forms it. One the maximum clamping pressure is achieved, the fluid pressure inside the tube is increased so that tube bulges to take internal shape of the die. Simultaneously additional cylinders axially compress the tube to prevent thinning and brushing swing expansion. It is possible that some parts of the component thin excessively during hydro forming. This can sometimes be rectified, in the case of tube hydro forming, by applying axial pressure to feed material into the bulges, thereby reducing bulging.

Tube Hydro Forming Process

Tube Hydroforming (THF) has been called with many other names depending on the time and country it was used and investigated. The first industrial applications for this process, namely the production of T-shaped joints, were published in papers in the 1960s; the use of these processes increased rapidly when in 1980sthe automotive industry turned its attention to this process and, more importantly, to the possibilities for light weight constructions. Throughout this paper, THF will be used to describe the metal forming process whereby tubes are formed into complex shapes with a die cavity using internal pressure, which is usually obtained by various means such as hydraulic, viscous medium, elastomers, polyurethane, etc., and axial compressive forces simultaneously.

Figure shows the process principles for tube hydroforming. A tube is placed in the tool cavity, whereby the geometry of the die corresponds to the external geometry of the produced part. These tools, in most cases separated in longitudinal direction, are closed by the ram movement of a press, and the tube ends are loaded by two punches moving along the tube axis. Each of the loads applied to the tube ends for sealing the tube’s interior must be at least equal to the force calculated from the product of the tube’s internal area and the tube’s internal pressure. However, the axial forces may be increased to a higher value if the forming job requires it. Then additional tube wall material is brought into the tool cavity. During the process the internal pressure is increased until the expanding tube wall comes into contact with the inner surface of the die cavity. This process principle may be used for hydroforming both straight and pre-bent tubes.

As shown in figure, the applicability of the process implies that failures caused by plastic instabilities such as buckling, folding and bursting can be excluded. The risk of buckling is posed as he start of the process by too high axial loads on the initial tube, and it is also present for the entire starting phase. So that this risk of buckling can be avoided by compensation the unsupported tube lenght with increasing in the section Modulus of the tube cross section through the simultaneous expansion of the tube wall.

In the intake zone of the expansion shape, a formation of folds cannot be avoided; these folds, which are symmetrical to the longitudinal axis, can be reversed by an increase in internal pressure during the final phase of the expansion process. However further folds can occur at the centre of longer expansion forms as a result of too high axial forces: these can be avoided with a proper process controller.

The risk of bursting is a result of too high internal pressure and is initiated by a local neck in the tube wall, whereby the onset of this local necking significantly depends on the initial tube wall thickness. To prevent this risk it must be ensured that the tube wall briefly comes into contact with the wall of the tool at the latest before the onset of necking.

Reference

1. Alessia Mentella, “Introduction to hydroforming process”, Università di Cassino.
2. John Godwin “Hydroforming techniques”.
3. Masaaki Mizumura, ET. al. “Development of hydroforming technology”, Nippon steel technical report no.90
4. M, Koç, Ed. By “Hydroforming for advanced manufacturing”, 2009 Woodhead Publishing Limited.
5.www.hydroforming.net
6.www.ultimatehydroforming.com
7. http://www.amalco.com/hydroforming.html

Whiplash Protection System

Abstract

During recent years the main focus in whiplash research has been on rear-end impacts. Rear-end impacts have the largest risk of whiplash injury and therefore much effort is being spent on decreasing this injury risk. The total number of frontal whiplash cases may be higher, despite the smaller risk. Therefore, it is clear that also in frontal impact there is a need for improvement of whiplash protection.

In the first European Whiplash project the rear impact loading phase was the main focus. The research at the time was mainly limited to the loading phase of rear impact, since most of the proposed injury mechanisms assume whiplash to occur in the loading phase. On the other hand, some of the mechanisms of whiplash injury are suggested to originate from the rebound phase of rear impact. The rebound phase involves neck flexion, as in frontal impact. Therefore, the current research aims at reducing whiplash in frontal and oblique impact and studies the rear-end rebound phase. In the end a test method will be proposed for evaluation of seats and restraint systems with respect to their whiplash protection. In this evaluation stage also a dummy is needed in order to assess the protection of a system. Part of the current project is to recommend on a dummy design that can be used for this purpose. Resulting from the findings in this concept, design guidelines for safer seat and restraint system design will be proposed.

Whiplash is a relatively common injury that occurs to a person's neck following a sudden acceleration-deceleration force, most commonly from motor vehicle accidents. Whiplash-a soft tissue injury to the neck-is also called neck sprain or neck strain. It is characterized by a collection of symptoms that occur following damage to the neck, usually because of sudden extension and flexion.

Hyperextension injury to the neck, often the result of being struck from behind, as by a fast moving vehicle in a car accident. Whiplash is a term used most often to describe the symptoms resulting from a car accident.

Whiplash Injury Reasons:

In order to understand how a whiplash injury occurs, you need to understand the structure of your body. The main support structure of your body is your spine, which consists of interlocking bones called vertebrae. Each vertebra is separated by a tough sack of jelly, called a disc.

In minor cases, the quick jerk to the neck will only result is some muscle damage, which can heal. In more severe cases, the whiplash motion can strain and sometimes even rupture the squishy discs that separate the vertebrae. When the disc gets damaged, the injured person may experience extreme pain, numbness, tingling, and other unpleasant sensations in the neck.

Whiplash Protection System

It is the type of protection system that had been implemented in the front seats of the four wheel vehicle in order to avoid the neck injury.

The WHIPS seat provides improved spinal support by virtue of its modified backrest characteristics and close proximity of the head restraint's position to the occupant's head.

WHIPS utilizes a specially designed hinge mount that attaches the back rest to the seat bottom

Principle of Whiplash Protection System

The Main Principle of Anti Whiplash Seat is to minimizing the degree of accident in the neck due to rapid movement of head and to design the seat's backrest and a head restraint that is sufficiently high and positioned close to the head are also important factors.

The principle is based upon the following parameters which has been explained below

1. The Principle of Active Head Restraints

Here when the force is exerted on the Seat from the head of the persons due to sudden acceleration, the special type of the mechanism in the restraints will helps avoiding the equal and opposite force that exerts from the seat

Before Exerting force After Exerting force

2.The Seat Design

The Seat will made up of Wire Frames which reduces the impact of the forces that exerts from the human body

3. Mechanism of the Seat

In an impact from the rear, immense force may be exerted on the vulnerable neck. The body is pushed forward and if the head does not accelerate together with the body, the neck can be over-stretched.

The 2005 Mercedes-Benz M-Class features an optional spring-activated system for whiplash protection. If the sensing system detects a rear collision within a specific impact severity, it releases pre-tensioned springs inside the head restraints. This causes the head restraints to move immediately forward by about 40 mm and upwards by 30 mm. This movement is designed to support the heads of the front seat occupants at an early stage, lowering the possibility of a whiplash injury.After activation, the head restraints can be unlocked and returned to the original position using a tool supplied with the vehicle. Mercedes-Benz plans on making this option available on all models in the future.

The pyrotechnic head restraint on the 2003 and newer BMW 7 Series is unique. On this system, a compressed gas cartridge at the base of the headrest frame activates during a rear collision, moving the headrest upward rather abruptly. The gas cartridge can be replaced, and the system reset if there is no further damage.

The initial concept was to develop a backset reducing active head restraint. For vehicle occupants it was observed that as the initial seatback angle increases, the separation point between the upper torso and seat back becomes lower. This is due to the occupant maintaining an upright head and torso posture. The idea was to develop a seat that conforms to the occupant prior to and during a rear impact at any seatback angle. Initial MADYMO model simulations showed that a modified head restraint would optimize its position relative to the occupants head. The concept seat model showed improved performance over a standard seat model. The results were directly due to the backseat being minimized.

Initial concept seat schematic .Upright seatback angle on the left and more inclined angle on the right. This seat design attempts to minimize seatback angles

This conforming seatback concept was carried through to the final concept design. Refinements to the design minimized the backset and also the torso to seatback gap. The concept seatback attempts to mimic the curvature of the spine and maintains close proximity to the thoracic spine. The head restraint is also positioned so that height and backset are optimal. Any initial seat back angle will result in a properly adjusted seat configuration. The result is a seat that conforms to the occupant in all seating positions.

Reference

1. The Prince of Wales Medical Research Institute Barker St.Randwick NSW 2031 Australia . By Michael Yuen, Mr.and Lynne E. Bilston, Dr.

2. Vernon HT, Dhami MS, Howley TP, Annett R, "Spinal manipulation and beta-endorphin-a controlled study of the effect of a spinal manip. on plasma beta-endorphin levels in normal males," J Manip. Physio. Ther. 1995, 18 (8).

3. Croft A, Freeman M, "Correlating Crash Severity with Injury Risk, Injury Severity, and Long Term symptoms in Low Velocity Motor Vehicle Collisions," Med Sci Monit, Vol. 11(10), 2005.

4. "Injury of the Anterior Longitudinal Liegament During Whiplash Situation, Eur Spine J, Vol 13, Jan/2004, Pg: 61-68. And, Batterman S, Batterman S, "Delta-V, Spinal Trauma, and the Myth of the 'Minimal Damage' Accident," J Whiplash & Related Disorders, Vol 1.

Robotic Car

Definition

We're pretty familiar with autonomous cars around here, and we've even been treated to a ride in one of Stanford's robots at their automotive innovation lab, which they launched in partnership with Volkswagen. You might also remember Shelley, their autonomous Audi TTS, which autonomously raced to the top of Pikes Peak last year. Volkswagen's thinking behind all of this high performance autonomous car stuff is that at some point, they'll be able to program your car to be a far, far better driver than you could ever be, and it'll have the ability to pull some crazy maneuvers to save you from potential accidents.

Google, who's just down the road from Stanford, seems to understand this, and they've turned their autonomous cars up to "aggressive" in this driving demo that they gave to some lucky sods in a parking lot at the TED conference in Long Beach. It's pretty impressive: This might seem dangerous, but arguably, this demo is likely safer than a human driving around the parking area at normal speeds, if we assume that the car's sensors are all switched on and it's not just playing back a preset path. The fact is that a car equipped with radar and LIDAR and such can take in much more information, process it much more quickly and reliably, make a correct decision about a complex situation, and then implement that decision far better than a human can.

This is especially true if we consider the type of research that is being done with Shelley to teach cars how to make extreme maneuvers, safely. So why aren't we all driving autonomous cars already? It's not a technical ; there are several cars on the road right now with lane sensing, blind spot detection and adaptive cruise control, which could be combined to allow for autonomous highway driving. Largely, the reasons seem to be legal: there's no real framework or precedent for yielding control of a vehicle to an autonomous system, and nobody knows exactly who to blame or sue if something goes wrong.

And furthermore, the first time something does go wrong, it's going to be like a baseball bat to the face of the entire robotics industry. Anyway, enough of the depressing stuff, here's an outside view of Google's robot car squealing around that parking lot: For what it's worth, "aggressive" is apparently one of four different driving personalities that you have the option of choosing from every time to start up one of their robot cars.

Lidar (Light Detection And Ranging) :

LIDAR (Light Detection And Ranging also LADAR) is an optical remote sensing technology that can measure the distance to, or other properties of a target by illuminating the target with light,often using pulses from a laser. LIDAR technology has application in geomatics, archaeology, geography, geology, geomorphology, seismology, forestry, remote sensing and atmospheric physics, as well as in airborne laser swath mapping (ALSM), laser altimetry and LIDAR Contour Mapping. The acronym LADAR (Laser Detection and Ranging) is often used in military contexts. The term "laser radar" is sometimes used even though LIDAR does not employ microwaves or radio waves and is not therefore in reality related to radar.

LIDAR uses ultraviolet, visible, or near infrared light to image objects and can be used with a wide range of targets, including non-metallic objects, rocks, rain, chemical compounds, aerosols, clouds and even single molecules. A narrow laser beam can be used to map physical features with very high resolution. LIDAR has been used extensively for atmospheric research and meteorology. Downward-looking LIDAR instruments fitted to aircraft and satellites are used for surveying and mapping. A recent example being the NASA Experimental Advanced Research Lidar. In addition LIDAR has been identified by NASA as a key technology for enabling autonomous precision safe landing of future robotic and crewed lunar landing vehicles. Wavelengths in a range from about 10 micrometers to the UV (ca.250 nm) are used to suit the target. Typically light is reflected via backscattering

Google Street View

Google Street View is a technology featured in Google Maps and Google Earth that provides panoramic views from various positions along many streets in the world. It was launched on May 25, 2007, originally only in several cities in the United States, and has since gradually expanded to include more cities and rural areas worldwide. Google Street View displays images taken from a fleet of specially adapted cars. Areas not accessible by car, like pedestrian areas, narrow streets, alleys and ski resorts, are sometimes covered by Google Trikes (tricycles) or a snowmobile. On each of these vehicles there are nine directional cameras for 360° views at a height of about 8.2 feet, or 2.5 meters, GPS units for positioning and three laser range scanners for the measuring of up to 50 meters 180° in the front of the vehicle.

There are also 3G/GSM/Wi-Fi antennas for scanning 3G/GSM and Wi-Fi hotspots. Recently, 'high quality' images are based on open source hardware cameras from Elphel. Where available, street view images appear after zooming in beyond the highest zooming level in maps and satellite images, and also by dragging a "pegman" icon onto a location on a map. Using the keyboard or mouse the horizontal and vertical viewing direction and the zoom level can be selected. A solid or broken line in the photo shows the approximate path followed by the camera car, and arrows link to the next photo in each direction. At junctions and crossings of camera car routes, more arrows are shown.

Interactive algorithms for path following involve direct communication with external sources such as receiving navigation data from the leader or consulting GPS coordinates. The Follow-the-Past algorithm is one such example; it involves receiving and interpreting position data, orientation data, and steering angle data from a leader vehicle]. The objective is to mimic these three navigational properties in order to accurately follow the path set by the leader. As orientation and steering angle are associated with GPS positional data, the following vehicle can update its navigational state to match that of the leader vehicle at the appropriate moment in time. One developed algorithm is best described as a placing a trail of breadcrumbs based on the leading vehicle's position . A cubic spline fit is applied to the generated breadcrumbs to establish a smooth path by which to travel. This developed algorithm was tested and showed centimeter-level precision in following a desired path

Safety Air Bags in Cars

Definition

For years, the trusty seat belt provided the sole form of passive restraint in our cars. There were debated about their safety, especially relating to children. But over time, mush of the country adopted mandatory seat-belt laws. Statistics have shown that the use of seat belts has saved thousands of lives that might have been lost in collisions. Air Bags have been under development for many years. The attraction of a soft pillow to land against in a crash must be very strong – the first patent on an inflatable crash-landing device for airplanes was filed during World War II. In the 1980’s the first commercial air bags appeared in automobiles.

Since 1988, all new cars have been required to have air bags on both driver and passenger sides (Light Trucks came under the rule in 1999). To date, Statistics show that air bags reduce the risk of dying in a direct frontal crash by 30 percent. Newer than steering Wheel mounted or Dashboard-mounted bags, but not so widely used, are seat-mounted and door mounted side air-bags. Some experts say that within the nest few years, our cars will go from having dual air bags top having six or even eight air bags. Having evoked some of the controversy that surrounded seat-belt use in its early years, air bags are the subject of serious government and industry research and tests.

Stopping an object’s momentum requires force acting over a period of time. When a car crashes, the force required to stop an object is very great because the car’s momentum has changed instantly while the passengers’ has not much time to work with. The goal of any supplemental restraint system is to help stop the passenger while doing as little damage to him or her as possible.

What an air bag wants to do is to slow the passengers’ speed to zero with little or no damage. The constraints that it has to work within are huge. The air bag has the space between the passenger and the steering wheel or dashboard and a fraction of a second to work with. Even that tiny amount of space and time is valuable, however, if the system can slow the passenger evenly rather than forcing an abrupt halt to his or her motion.

Development of Air Bags:

The idea of using a rapidly inflating cushion to prevent crash injuries has a long history. The first patent on an inflatable crash-landing device for airplanes was filed during World War II.

Early efforts to adapt the air bag for use in cars bumped up against prohibitive prices and technical hurdles involving the storage and release of compressed gas.

• If there was enough room in a car for a gas canister.
• Whether the gas would remain contained at high pressure for the life of the car.
• How the bag could be made to expand quickly and reliably at a variety of operating temperatures and without emitting an ear-splitting bang.

They needed a way to set off a chemical reaction that would produce the nitrogen that would inflate the bag. Small solid-propellant inflators came to rescue in the 1970’s.

In the early days of auto air bags, experts cautioned that the new device was to be used in tandem with the seat belt. Seat belts were still completely necessary because airbags worked only in front-end collisions occurring at more than 6 Kmph. Only Seat belts could help in side swipes and crashes (Although side-mounted air bags are becoming more common now), rear end collisions and secondary impacts. Even as the technology advances, air bags still are only effective when used with a lap/Shoulder seat belt.

Construction of Air Bags:

Airbag are assemblies consisting of the airbag (made of Nylon), inflator modules and sensor housing, electrical connectors (Clock spring), airbag retainer and the cover. The driver's side bag is mounted in the center of the steering wheel as shown in fig. 1.

Fig. 1 Driver's side bag

SENSOR TYPES

Ball and Magnet Type Sensor

Fig. 2 Ball and Magnet Type Sensor

 

Spring and Roller type

Fig. 3 Spring and Roller type

By function, there are 2 types- Impact sensors and safing sensors. The Forward sensors are located in various locations forward of the passenger compartment. Some are located inside the fenders, some are on the cowl, and some are attached to the core support in front of the radiator.

Rear Sensors are also known as safing sensors as their functions is to determine that a crash has occurred. Rear safing sensors are located in various locations in the passenger compartment depending on the manufacturer. Some are integrated with the control/Diagnostic Module.

The Rear safing sensor must close before the forward sensors to avoid airbag deployment in cases where the impact is not severe enough to cause deployment. When the vehicle is parked with ignition off deployment is very unlikely because there is no power to the circuits for deployment this means that someone can hit your car and sound the alarm but not deploy the airbags.