During various impacts, body parts receive deformation, which sometimes cannot be visually determined
Therefore, for more accurate editing of the body and assessment of deformation, one should be guided by reference dimensions.
Reference points are shown in Figure 1.
The frame design is calculated so that upon impact from either side, the impact energy is extinguished.
The body parts that form the interior must receive the minimum possible deformation, in other words, the body must eliminate or reduce the severity of the consequences of the accident.
Bumpers are used to absorb impact energy in a collision. To ensure safety inside the cabin, there is a soft instrument panel, rack linings, and the design of other elements.
Seat belts also play a role in safety.
The body frame includes the following elements: front, floor, sidewalls, roof with windscreen frame, rear panel and load-bearing elements - side members, cross members, racks.
Plumage details: front body panels and attachments - hood, tailgate, front fenders.
All parts and assemblies, except for hinged elements and front fenders, are connected by resistance spot welding, and heavily loaded frame parts are additionally welded by electric arc welding.
The front end consists of a vertical shield, mudguards, crossbars, an air intake box, amplifiers and other small parts. Mudguards are connected to the front spars.
Car floor includes front, middle and rear floors.
In the front, which has a trough-shaped form, there is a tunnel for placing exhaust pipes, fuel and brake pipelines.
The tunnel serves to protect these parts from damage and increase the rigidity of the floor.
Spars are welded along the floors. The front, middle and rear crossbars are also welded to the floor.
The sidewalls of the body consist of external and internal panels. The outer ones are one-piece with B-pillars, C-pillars and side window openings.
The inner body panels constructively combine the outer arches of the rear wheels and the strut reinforcements.
Behind the amplifier, at the right sidewall, there is a niche for installing a gasoline vapor trap, grooves and flanges for door and glass seals.
Removable components are doors, tailgate, hood, front fenders, bumpers, grille, etc.
The wings are attached to the frame with self-tapping bolts; pads are installed under the wings to reduce vibration. The hinges of the front doors and the hood can be adjusted.
To increase the rigidity and strength of the body, reinforcing pads, brackets, stiffeners are used.
To protect against mechanical damage, create thermal and noise insulation, the lower outer part of the body, the mudguards of the wheels and the inner surfaces of the wings are covered with anti-corrosion material, and the floor of the passenger compartment and trunk are covered with special vibration-damping mastics.
Before welding places subject to corrosion, the parts to be welded are coated with a special preservative compound.
The outer and inner surfaces of the body are treated with special compounds, as a result of which water-insoluble protective compounds are formed on them. Outside, the body is painted with synthetic enamels.
Safety-enhancing body parts
The most probable speed of vehicles in collisions is 80 km/h in frontal and rear impacts and 64 km/h in side impacts.
These figures are the starting point for calculating the strength of bodies and developing constructive measures to ensure the safety of passenger cars.
Improving vehicle safety includes "active" safety measures that help prevent accidents, and "passive" safety measures that are built into the design of the car to ensure the safety of the driver and passengers if an accident cannot be prevented.
Measures of "active" safety of the car provide for the development of designs of parts and assemblies that ensure the efficiency of braking and the reliability of the brake drive, anti-lock systems that allow the car to move in a given m direction when braking, as well as measures to increase the visibility of the road and the environment from the driver's seat.
This includes the installation of a dual-mode wiper, heater, fan, which prevent icing and fogging of windows.
Measures of "passive" safety provide for the prevention or reduction of injuries to the driver and passengers in the event of an accident.
The result is achieved by providing a protective zone around each passenger, limiting the ability of the driver and passengers to move relative to the seat, reducing the level of injuries from impacts on the internal surfaces of the passenger compartment, providing the opportunity for the driver and passengers to exit the crashed car.
Ensuring the protective properties of the body consists in the development and implementation of such design solutions that allow you to form a protective zone around the driver and passengers.
The rigid interior combined with energy-absorbing front and rear bodywork reduces the acceleration of people at the moment of impact and provides the best possible protection zone around passengers.
Bodies of this design are built on the principle of progressive energy intensity, i.e. with a given degree of reinforcement of some parts with the maximum allowable collapse of others in order to absorb impact energy.
Very heavy impact loads in different directions (longitudinal, transverse and vertical) act on doors, door hinges and door locks.
The doors protect the passenger compartment from entry of foreign objects in the event of an accident and should not be opened during a collision so that passengers cannot fall out of the body.
Door locks are equipped with a reliable locking system that prevents them from being accidentally unlocked under the action of inertial loads or upon impact at the time of an accident, since the doors themselves are not excluded from the general contour of the rigidity of the body interior.
To protect the driver and passengers in side collisions, box-section protective bars are built into the body doors.
The beam is placed inside the door between the sliding glass and the outer panel.
In addition to protecting the interior from the penetration of the hitting car, the bars seem to move the hit car to the side.
Bumpers in modern passenger cars have protective properties combined with decorative features created by designers.
Today, wide profile bumpers with the most rounded shapes are installed. Their protective properties are high, the bumpers protect the car from damage in light collisions and must comply with international safety standards.
Systems that limit the movement of the driver and passengers inside the body include seats and seat belts.
The level of injury during accidents is reduced most effectively if the design of the car provides for a reliable fastening of the passenger to the seat, which, in turn, should not come off the floor of the body under the action of emergency overloads.
Seats are secured to withstand safety requirements for longitudinal loads acting in both directions, as well as for torque.
The seat belts have a simple locking device that provides a secure fastening and, if necessary, allows you to quickly unfasten.
In the working position, the belts provide sufficient freedom of movement for the driver and do not interfere with driving.
Calculations and practice show that seat belts reliably protect passengers in a frontal collision at speeds up to 80 km/h.
The next element is the steering wheel. The safety of the steering wheel is to exclude cases of severe injury to drivers in frontal collisions of cars.
In accordance with the requirements, during a collision test of a car with a reinforced concrete barrier weighing at least 70 tons at a speed of 48.3 km / h, the upper part of the steering column and steering shaft should not move in the rear direction horizontally and parallel to the longitudinal axis of the vehicle for more than than 12.7 cm.
If the steering column collides with a torso model that strikes the column at a relative speed of at least 24.1 km/h, the force exerted by the steering column on the front of the torso model must not exceed 11.35 kN ( 1135 kgf).
Vehicle windshields must comply with UNECE regulations.
For example, the windows of VAZ cars are three-layer, they consist of two profiled polished glasses with a layer of sticky transparent plastic.
The main advantage of a laminated windshield is that cracks propagate from the center of impact upon impact, fragments are held on a plastic layer, the glass retains its transparency, shape and does not fall out of the body opening.
The rear and side windows are made of tempered glass and are specially heat treated for increased strength.
When broken, these glasses break into many small fragments without sharp corners and edges that can cause deep injuries.
Head restraints should exclude severe injuries, expressed in damage to the cervical vertebrae and vertebrae of the upper chest.
Such injuries are caused when a moving vehicle hits the back of a stationary vehicle.
In this type of traffic accident, the strength of the head restraints must comply with international UNECE rules, and their design should exclude the possibility of injury to the rear passenger in a frontal collision of cars.
The interior of the body is important.
It includes interior trim, which should meet modern aesthetic and ergonomic requirements.
The instrument panel is made without protruding parts and sharp edges, with convenient placement of instrumentation and controls.
The energy intensity of the panel is ensured not only by soft upholstery, but also by the introduction of steel thin-sheet panels into the structure of the frame, capable of absorbing energy upon impact due to their partial deformation.
Armrests, doors and sun visors are lined with soft materials.
Door handles, power windows, switch buttons and door locks are placed and manufactured so that in the event of an impact, the passenger could not be injured.
Car accident damage
The greatest number of collisions of cars falls on the front, somewhat less on the back and the least on the sides.
Crash damage to bodywork is divided into three categories. The first includes very severe damage, as a result of which the replacement of the body is necessary.
The second category includes moderate damage, in which most of the parts require replacement or complex repairs.
The third includes less significant damage - holes, tears in the front panels, dents and scratches received during impact while driving at low speed.
These damages do not pose a danger to passengers and the driver during the operation of the car, although its appearance does not meet aesthetic requirements.
The most destructive damage to the body is observed during frontal collisions - collisions inflicted on the car directly into the front of the body or at an angle of no more than 40–45 ° in the area of the front pillars.
Such collisions usually occur between two vehicles moving towards each other, the speeds of which are added together, which creates high shock loads.
The amount of energy that must be absorbed during such collisions is enormous: about 80,100 kJ for a car weighing about one ton.
This energy is absorbed when the car deforms in less than 0.1 s.
The body of the car is destroyed, especially its front part, and the large loads acting in this case in the longitudinal, transverse and vertical directions are transferred to all adjacent parts of the body frame and especially to its strength elements. Consider what was said with examples.
So, the frontal collision of the car occurred with the front part of the body in the area of the left front fender, side member and left headlight.
The bulkhead panel, fenders, hood, mudguards, front spars, windscreen frame and roof receive devastating damage.
This deformation is set visually.
Invisible deformation occurs in the A-pillars, B-pillars and C-pillars on both sides, in the left front and rear doors, in the left rear fender and even in the rear trunk panel.
Or: the collision occurred with the front of the car body at an angle of 40-45°.
The front fenders, hood, front panel, mudguards, front spars received devastating damage.
It is almost impossible to restore the base points of the front part of the body without replacing the deformed parts with new ones.
In this case, it is necessary to restore the dimensions of the front door openings and the position of the front and central pillars, so how force loads were transferred through the front doors to the A-pillars and B-pillars, creating compressive forces on the sill and upper body sidewall.
Another example: a blow was struck from the side to the front of the car body in the area where the front panel mates with the front parts of the side member and the left wing.
Destructive damage is received by both front fenders, front panel, mudguards, spars, hood.
Tension forces break the left front door opening, compressive forces cause deformation in the right door opening and in the side of the left front door.
The front and center pillars also receive significant force overloads and deviate from their original position.
The blow was received from the side into the A-pillar of the car on the left side.
At the same time, the left front pillar, wind window frame, roof, floor and front floor side members, front panel, hood, fenders, mudguards and front side members are significantly deformed.
The front of the car body moved to the left, the threshold and the upper part of the right sidewall took tensile loads, and the central and rear pillars took compressive loads; the right mudguard in conjunction with the front pillar experienced tearing forces.
During an external examination of the emergency body, it is possible to establish the presence of distortions in the extension or retraction of the doors, trunk lid and hood relative to the fixed surfaces of the body parts.
Violation of the uniformity of the gaps along the junction lines of mounted and fixed parts also indicates the presence of deformations in the parts of the body frame caused by the accident.
It should be remembered that by external inspection it is impossible to determine the deviations of the linear dimensions of the body openings and geometric parameters according to the base points of the body base. For these purposes, it is necessary to use measuring instruments.
Damage to the body during operation
We are talking about less significant damage to the body that occurred during the operation of the car and worsens the appearance.
Dents appear as a result of permanent deformation upon impact, improper repair, and also due to poor-quality bodywork.
Dents can be simple and easily repairable and complex - with sharp bends and folds or located in places that are difficult to repair.
Cracks are common body damages.
They can appear anywhere as a result of overstressing of the metal (shocks, bends), as well as as a result of weak connection of components and parts and insufficient structural strength.
Ruptures and holes are divided into simple ones, which take the form of a crack after straightening the metal, and complex ones, requiring patching when repairing a damaged patch.
Cliffs in body parts are characterized by the size of the torn part of the panel or plumage.
Large breaks are often eliminated by setting inserts of a complex profile, and in some cases a complete replacement of the part is made.
Expanded metal surfaces are distinguished by their location: on the surface of the panel in the form of a bump and in the flanging of parts (sides and edges are stretched).
Corrosion in its external manifestation can occur in the form of uniform, when the metal is destroyed evenly over the entire surface, and local, when the metal is destroyed in separate areas.
The latter form of corrosion is detected by dark spots or deep black dots on the metal, it is more dangerous, since the metal can collapse in a short time with the formation of through holes.
Faulty welds occur in spot-welded parts and solid body welds.
Riveted joint failure is the result of loosening or shearing of rivets, as well as wear of bolt holes and rivets.
Deflections, warps and twists are usually the result of accident loading. Distortions can be internodal and in the plane of one node or part (distortion in the doorway of the body, distortion in the door itself, floor deflection).
Hole and pin wear results from rolling friction (pins and holes in door hinges) or loosening of the assembly with rivets or bolts; wear of surfaces - due to the systematic load applied to the surface, for example, when transporting abrasive loads in the back of a car.
When repairing cars, two main areas of dimensional control are used: mechanical systems (wupy, tape measures, templates, etc.) and optical systems that project a laser beam onto control points.