There is a strange notion that frontal impact speeds add up. In the news about some accident, a police representative said that the speed of the cars was 100 km / h, which means a total of 200 km / h. Well, yes, in total: 100 + 100 = 200. You can't argue. And then what?
Interesting, of course, are not the numbers, but the real consequences of the strike. And you need to compare not just 100 and 200, but, for example, the consequences of a collision with a concrete wall. So, in a head-on collision of two identical cars at the same speed of 100 km/h, each effect for either of these two cars will be, as many believe, the same as hitting a concrete wall at 200 km/h. And this is a very dangerous delusion, in my opinion. The effect will be the same if you drive into a concrete wall at 100 km/h. Exactly 100, not 200!
In general, the thoughtless addition of numbers resembles the cartoon "Squad America: World Police". In it, about some terrible terrorist attacks, they said something like: “It will be 10 times worse than 9/11.” Then someone said: “9110 is some kind of horror!!”. I can't vouch for accuracy, but the meaning has not changed. 911 what? 9110 what? So here - 200 km / h of what? Relative to the Sun, we generally move at a speed of 30 km / s, and nothing. Moreover, if you accelerate to 200 km / h and then slow down smoothly, what will happen is not the same as sharply vtemyashitsya into a concrete block. Those. It's not the speed that's important, it's the timing of that speed. The maximum acceleration experienced by occupants of the vehicle during braking, impact, etc.
Probably, thoughts about the addition of velocities come to mind in connection with residual memories from physics. But there, no one adds speed thoughtlessly. There is conservation of energy, there is conservation of momentum. There are accelerators on colliding beams. But we are not interested in the behavior of systems of bodies, but in the “sensations” of one body. The sensation of the body will just be the maximum acceleration, and not total energy-mass-momentum.
In the case of a collision with a concrete block and in the case of a collision with an oncoming car, from a practical point of view, it can be assumed that the speed extinction time will be the same. And the acceleration will be the same. This means that it makes no difference what to drive into - a concrete block or the same car traveling to a meeting at the same speed. There are no additions of velocities here and cannot be. This is a delusion, and a very dangerous one, it is now easy to see.
Of course, you need to understand that a sliding blow is better than a direct frontal one. That instead of an oncoming strike, it is better to prefer a hit on a passing car - it is softer. That a hit on a passing car is softer than a hit on a “passing” concrete block. In general, it is important to understand what dangers lurk on the road, and to see which of them are more terrible and which are less. To save your life, your health will have to make a choice. Knowledge is required to make an informed choice. But they don't give us. But what can I say: even traffic police officers, people who are directly related to traffic safety, don’t even have them.
Undoubtedly, any accident is an extremely unpleasant incident, which often ends in tragedy. However, no matter how much the parties would like to quickly forget everything, in any case, it is necessary to identify the culprit and assess the damage caused. The correct classification of the type of accident and the reconstruction of the overall picture of events, part of which is the speed of both cars, can help in performing such a task.
Calculation of speed, and how a head-on collision occurs
Many motorists believe that when two cars collide head-on, their speeds are summed up, and final result will be the same as in the case of a collision of one car at a total speed against a concrete wall.
That is, suppose that two vehicles before the collision were moving at a speed of 65 km / h each, but would this mean that one such vehicle crashing at a speed of 130 km / h into a concrete wall would receive the same damage as the cars in the previous version? Do speeds add up in a head-on collision? Let's try to understand this issue.
In a collision of vehicles, everything happens literally in a matter of seconds, during which each of the cars is deformed or completely destroyed. The main factors influencing the force of destruction are the design of the machines and their speed, and the impact impulse acts along the line of impact. The direction of this line during the collision depends on the direction and speed of movement of the two bodies. If the vehicles were moving different speeds, then the line of impact will pass at a smaller angle with respect to the axis of the machine moving at a higher speed.
At the same time, considering the collision of a vehicle with an obstacle, two subsequent stages can be distinguished in this process: moment of contact(counted until the moment of closest approach) and moment of vehicle movement, which lasts until the separation of the cars. The first stage is characterized by a partial transition of the kinetic energy of motion into potential thermal energy, elastic deformation energy, etc. With the beginning of the second stage, the resulting potential energy of deformation is again transformed into the kinetic energy of the vehicle. If we are talking about inelastic bodies, then the impact will end already at the first stage.
Even if we assume that the car was moving at a low speed, its kinetic energy will be quite large, and hitting a stationary wall with a large mass will lead to the absorption of all its energy. The strong and rigid wall is almost not deformed.
Of course, it cannot be said that hitting a stone wall will be completely identical to the collision of two identical cars. Eg, if one vehicle is moving faster than the other, then the total energy released during the collision will be less than that in the previous case. More light car or a vehicle traveling at a slower speed will receive more energy than they had before the collision. That is, when figuring out whether the speed is summed up in a head-on collision, it is necessary to understand that it is not this indicator that needs to be added, but the impulses - a combination of speeds and masses.
Energy is spent on deformation (accompanied by heat release) and elastic deformation with a change in momentum (velocity modulo direction). The balance of these deformations is determined by the initial conditions of the accident, and the final result is based on the balance of the occurring deformations. Thus, there is a damping of impulses.
Common Causes of Frontal Car Collisions
If you are interested in how you can avoid a head-on collision, then it is useful to know about possible reasons, which lead to such trouble. So, in most cases, a collision of vehicles is the result of overtaking with a drive into the oncoming lane, bypassing various obstacles (including other parked cars), crossing intersections (especially roundabouts), as well as a consequence of advancing with moving to the extreme left lane and rebuilding.
Also, one cannot help but recall the excess speed limit, which is also common cause creating accidents on the roads. This behavior is especially dangerous if the motorist does not have basic driving skills, as a result of which the car may tip over (especially true for icy conditions).
Note!According to the information provided by the traffic police, most of the head-on collisions occur in winter period when the road surface is covered with ice crust, and drivers are unprepared for such weather conditions.
Often the root cause of an accident is also the excessive self-confidence of drivers. Having decided to overtake a vehicle moving in front, not all motorists correctly estimate the speed of a car traveling along oncoming lane, and passing vehicles. In addition, various optical effects resulting from limited visibility and bad road conditions.
A frequent cause of head-on collisions of cars can also be called the fatigue of the driver, who simply falls asleep at the wheel and unconsciously directs his vehicle into the oncoming traffic lane. This often happens to drivers of oversized trucks, and you can understand that a person is sleeping at the wheel based on the dynamics of acceleration of the car in the oncoming lane and the trajectory of its movement.
Interesting to know!The foreign edition of Forbes calls drunk drivers the main cause of frontal accidents. It's no secret that not even a large number of alcohol in a person's blood significantly reduces his reaction to everything that happens, which is why in the same America there is half of all accidents on the roads.
As for domestic motorists, it is safe to say that this is far from the only reason for the growth of accidents on the roads. The driver may also lose control of the vehicle due to a skid, steering lock or driving onto a bad stretch of road.
So how do you get away from a head-on collision on the highway if an uncontrolled car is rushing at you? The main thing is to try to avoid hitting head-on, because in this case, damage to the car and injuries to passengers are often more significant than in other types of collisions (for example, when hitting a tangent). Therefore, the first thing to do in an unforeseen situation is to slow down and try to slow down, and only then begin to operate the steering wheel.
However, if you see that a head-on collision is still imminent, it is better to point the car away from the road. In any case, entering a bush, ditch or snowdrift will be less dangerous than meeting oncoming traffic (of course, large trees, poles or walls are also best avoided).
Important!In a frontal impact, the airbags do not deploy, so the only thing that can save the driver and passengers is the seat belt.
In addition, as soon as you notice that an oncoming car has left its lane and is almost next to your car, it is better to prefer a tangent collision with a passing one to a frontal impact vehicle. This advice is also relevant for situations when an unexpected obstacle appears on the road (for example, a large animal), and you have no way to avoid meeting it.
A fairly large number of severe or even fatal injuries occur as a result of blows to the sides of the vehicle. In the event that you did not immediately notice a car approaching from the side, and stopping your own vehicle will definitely lead to a collision, you can also try to get away from it by increasing the speed. You need to understand that an attempt to prevent a head-on collision with one car can always end up with a meeting with another.
Did you know? According to the official statistics of the traffic police of Russia, in the first half of 2016 (from January to June) more than 8,000 people died in road accidents, and 34.3 thousand accidents were caused by low quality pavement. Compared to last year, the growth of such accidents amounted to 7.8%.
What to do if a collision is unavoidable
Due to confusion, many drivers do not have time to react to the danger that has appeared, and it is often too late to take any action to avoid a collision with a car flying at you.
What to do in a head-on collision? In fact, you have few options, and in addition to the actions already described, the main of which is an attempt to avoid a head-on strike, all that remains for you is to warn the other participants traffic about emergency. It is likely that a sound or light signal will also affect the driver of an oncoming vehicle, bringing him out of his stupor. So, a loud signal heard at such moments acts as an irritant that can bring a confused or tired person to life.
However, if the driver rushing towards you has lost control of his vehicle, then in this way you will only be able to warn other drivers of an imminent accident, although this is already a lot.
Well, if in a critical situation you were fastened, but if this is not the case, try to quickly lie on your side, moving into the passenger seat - this will save you from dangerous injuries from flying objects. The seated driver also needs to cover their face with their hands, which will help protect their eyes and face from broken glass fragments, as well as quickly remove their feet from the pedals (this way you will save yourself from serious fractures of the feet and lower legs).
Be that as it may, but in any situation, it is worth remaining calm and not succumbing to panic. Only in this way will you be able to navigate and do everything possible to minimize the possibility of damage.
Note! Conversation by mobile phone in the process of driving a vehicle increases the risk of an emergency by four times, and if the driver also thought of typing messages, then the probability of receiving damage in a head-on collision increases by as much as six times. The reaction speed of the driver in such a situation is reduced by 9% and 30%, respectively.
To understand the scale of car damage after an accident, one must clearly understand what happens directly at the moment of impact with the car body, which areas are subject to deformation. And you will be unpleasantly surprised to know that in a frontal impact, the rear of the body is skewed.
Accordingly, after an unfair body repair front part, even if the car was on the slipway, you will observe jamming of the trunk lid, chafing sealing gum and much more. If you are interested in this topic, I suggest that you familiarize yourself with educational material on the theory of collisions, which was prepared by the specialists of our training center.
General information
Theory clashes – This knowledge And understanding forces, emerging And existing at collision.
The body is designed to withstand impact from normal traffic and ensure the safety of passengers in the event of a vehicle collision. When designing a body Special attention given to it to deform and absorb maximum amount energy in a severe collision and at the same time had minimal impact on passengers. For this purpose, the front and rear parts of the body must be easily deformed to a certain extent, creating a structure that absorbs impact energy, and at the same time, these parts of the body must be rigid in order to preserve the separation area for passengers.
Determination of violation of the position of body structure elements:
- Knowledge of collision theory: understanding how the structure of a car reacts to the forces generated in a collision.
- Body inspection: search for signs indicating damage to the structure and its nature.
- Taking measurements: the main measurements used to detect violations of the position of structural elements.
- Conclusion: applying knowledge of collision theory together with results external examination to assess the actual violation of the position of the element or elements of the structure.
Collision types
When two or more objects collide with each other, the following collision scenarios are possible
According to the initial relative position of objects
- Both objects are moving
- One is moving and the other is stationary
- Additional collisions
Direction of impact
- Front collision (frontal)
- Collision from behind
- side impact
- rollover
Let's consider each of them
Both objects are moving:
One is moving and the other is stationary:
Additional collisions:
Front impact (frontal):
Rear Collision:
Side impact:
Rollover:
Influence of inertial forces in a collision
Under the influence of inertia forces, a moving car tends to continue moving in forward direction and when it hits another object or vehicle, it acts as a force.
A car that is stationary tends to remain stationary and acts as a force to counteract another car that has run over it.
When colliding with another object, an "External Force" is generated
As a result of inertia, "Internal Forces" arise
Damage types
Force and impact surface
Damage will be different for given vehicles of the same weight and speed, depending on the collision object, such as a pole or wall. This can be expressed by the equation
f=F/A
where f is the magnitude of the impact force per unit surface
F - strength
A - impact surface
If the impact is on a large surface, the damage will be minimal.
Conversely, the smaller the impact surface, the more severe the damage will be. In the example on the right, the bumper, hood, radiator, etc. are seriously deformed. The engine is moved back and the consequences of the collision reach the rear suspension.
Two types of damage
Primary Damage
The collision between the vehicle and the obstacle is called primary collision, and the resulting damage is called primary damage.
Immediate Damage
Damage caused by an obstacle (external force) is called direct damage.
Wave Effect Damage
The damage created by the transfer of impact energy is called ripple effect damage.
Caused damage
Damage caused to other parts subjected to tensile or pushing force as a result of direct damage or wave effect damage is called induced damage.
Secondary Damage
When the vehicle hits an obstacle, a large deceleration force is generated that brings the vehicle to a halt within a few tens or hundreds of milliseconds. At this point, passengers and objects inside the car will try to continue their movement at the speed of the car before the collision. A collision that is caused by inertia and that takes place inside the vehicle is called a secondary collision, and the resulting damage is called secondary (or inertial) damage.
Categories of violation of the position of parts of the structure
- Forward bias
- Indirect (indirect) displacement
Let's consider each of them separately
Forward bias
Indirect (indirect) displacement
shock absorption
The car consists of three sections: front, middle and rear. Each section, due to the peculiarities of its design, reacts independently of the others in a collision. The car does not react to impact as one inseparable device. On each section (front, middle and rear), the effect of internal and (or) external forces is manifested separately from other sections.
Places where the car is divided into sections
Crash shock absorption design
The main purpose of this design is to effectively absorb the impact energy of the entire body frame in addition to the destructible front and rear parts of the body. In the event of a collision, this design provides a minimum level of deformation of the passenger compartment.
Front body
Since the collision probability for the front end of the body is relatively high, in addition to the front spars, upper wing apron reinforcements and upper side panels body dashboard with stress concentration zones designed to absorb impact energy.
Rear body
Due to the complex combination of rear side panels, rear floor box and elements welded with spot welding, the impact absorption surfaces are relatively difficult to see in the rear, although the concept of impact absorption remains similar. Depending on the location fuel tank the impact absorption surface of the rear floor spars has been modified to absorb impact energy from collisions without damaging the fuel tank.
The ripple effect
Impact energy is characterized by the fact that it easily passes through the strong areas of the body and finally reaches the weaker areas, damaging them. This is based on the principle of the wave effect.
Front body
IN rear wheel drive car(FR), if impact energy F is applied to leading edge A of the front spar, it is absorbed by damaging zones A and B and causes damage to zone C as well. The energy then passes through zone D and after a change of direction reaches zone E. Damage generated in zone D, shown by the rear offset of the spar. The impact energy then causes ripple effect damage to the instrument panel and floor box before spreading over a wider area.
In a front-wheel drive vehicle (FF), the energy of a frontal impact will cause intense destruction of the front part (A) of the side member. The impact energy, causing the rear section B of the spar to bulge, eventually leads to damage to the instrument panel (C) from the ripple effect. However, the ripple effect on the rear (C), reinforcement (lower rear of the spar) and steering bracket (lower instrument cluster) remains negligible. This happens because central part the spar will absorb most of the impact energy (B). Another characteristic front wheel drive car(FF) is also damage to engine mounts and adjacent areas.
If the impact energy is directed towards section A of the wing apron, the weaker sections B and C along the path of the impact energy will also be damaged, providing some of the energy to be canceled as it propagates backwards. After zone D, the wave will act on the top of the pillar and roof rail, but the impact on the bottom of the pillar will be negligible. As a result, the A-pillar will tilt back, with the bottom of the A-pillar acting as a pivot point (where it connects to the panel). A typical result of this movement is a shift in the seating area of the door (the door becomes misaligned).
Rear body
The impact energy on the rear side panel causes damage at the contact area and then at the tailgate. Also, the rear side body panel will move forward, eliminating any gap between the panel and the tailgate. If higher energy is applied, backdoor may be pushed forward, deforming the B-pillar, and damage may extend to the front door and A-pillar. Door damage will be concentrated in the folded areas at the front and rear of the outer panel and in the door lock area of the inner panel. If the rack is damaged, then a typical symptom is a poorly closed door.
Other possible direction wave effect is the path from the tailgate pillar to the roof rail.
In this case rear end roof rail will push up, creating more clearance at the rear of the door. Then, the junction of the roof panel and the rear side of the body is deformed, leading to deformation of the roof panel above the B-pillar.
Among motorists there are a lot of plausible myths that a large number of people believe in. We have already written about many myths on the pages of our publication. Today we want to talk about the most common myth - about the addition of the speeds of two cars in a frontal impact. Let's dispel this myth once and for all.
Somehow it so happened that many people believe that if two cars collide head-on, then the impact energy will correspond. That is, as many motorists believe, in order to understand how strong a frontal impact will be, you need to add up the speeds of both cars involved in an accident.
To understand that this is a myth, and to calculate the force of a frontal impact and the consequences for cars involved in such an accident, we need to make the following comparison.
So let's compare the effects on cars in various accidents. For example, each car is moving towards each other at a speed of 100 km/h, and then they collide head-on. Do you think the consequences of a frontal impact will be more serious than from at the same speed? Based on a common myth that has been circulating for several decades among people who only half know physics (or are not familiar with it at all), then at first glance the consequences of a frontal impact of two cars at a speed of 100 km / h will be more deplorable than car at the same speed brick wall, since the alleged force of the frontal impact will be greater due to the fact that the speeds of the cars in this case need to be added. But it's not.
In fact, the force of a frontal impact of two cars at a speed of 100 km / h will correspond to the same force as when they hit a brick wall at a speed of 100 km / h. This can be explained in two ways. One is simple, which even a schoolboy will understand. The second is more complex, which not everyone will understand.
SIMPLE ANSWER
Indeed, the total energy that must be dissipated by crushing the metal of the body is twice as high when two cars collide head-on than when one car hits a brick wall. But in a head-on collision, the distance of crushing the metal of the bodies of both cars increases.
Since the bend in the metal is where all this energy is going to be absorbed twice as much as it will be absorbed by two cars, as opposed to hitting a brick wall where the kinetic energy will be absorbed by one car.
Thus, the deceleration rate and force of a frontal impact at a speed of 100 km/h will be approximately the same as when hitting a brick immovable wall at 100 km/h. Therefore, the consequences for two cars moving at the same speed and colliding head-on will be about the same as if one car crashed into a stationary wall at the same speed.
MORE DIFFICULT ANSWER
Let's assume that the cars have the same mass, the same deformation characteristics and perfectly at right angles collide head-on and do not fly far from each other. Let's say both cars stop at the collision point. Thus, moving, for example, at a speed of 100 km/h, each car will stop on impact from 100 to 0 km/h. In this case, each car will behave in exactly the same way as if each of them collided with a stationary wall at a speed of 100 km / h. As a result, both cars will receive the same damage in a perfect frontal impact as if they hit a wall.
To understand why exactly the same damage, you need to conduct a thought experiment. To do this, imagine that two cars are traveling at a speed of 100 km/h towards each other. But on the road between them there is a thick, very strong, immovable wall. Now imagine that both cars simultaneously crash into this imaginary wall from opposite sides. Each at this moment simultaneously stops from 100 km / h to 0 km / h. Since the wall on the road is very strong, it does not transfer the impact energy from one car to another. As a result, it turns out that both cars hit a standing wall separately, without affecting each other.
Now repeat this thought experiment with a thinner and not very strong wall, but able to withstand the blow. In this case, if the blow is from two sides at the same time, the wall will remain in place. Now imagine instead of a wall a sheet of a durable piece of rubber. Since two cars hit it at the same time, the rubber sheet will stay in place since both cars will hold the rubber in place at the same time they hit it. But a thin sheet of rubber cannot slow down any car, so even if you remove a sheet of rubber between cars that collide head-on, each car still stops at the moment of impact from 100 km / h to 0 km / h, that is just as if one car crashed into a solid, immovable wall at a speed of 100 km / h.
Is the impact energy and consequences the same in a collision with a stationary car or a stationary wall?
This is another common myth among motorists, which is related to the fact that if, for example, at a speed of 100 km / h, you collide with parked car, then the impact force will be exactly the same as if the car flew into a stationary wall at a speed of 100 km / h. But this is not so either. This pure water a myth that is based on ignorance of elementary physics.
So, imagine the situation that one car is moving at a speed of 100 km / h and at full speed collides with exactly the same car standing on the road. At the moment of impact, one car, continuing its movement, will push the other car. As a result, both cars will fly away from the collision site. At the moment of impact, the kinetic energy will be absorbed by the deformation of the body of both cars. That is, the impact energy will also be shared between the two cars. In the case of a blow to a fixed wall of one car at a speed of 100 km / h, only one car will have deformation of the body. Accordingly, the impact force and its consequences for the car will be greater than when hit at the speed of one car into another, which is standing still.
