Vehicles Over Elastic Suspensions

Question 1

51) What does it lead to the elastic interconnection of both wheels of each side of a two axle vehicle? a. To a reduction of roll in static or quasi-static conditions, but also to a decrease of the relative natural frequency;
b. To a reduction of pitch in static or quasi-static conditions, but also to an increase of the relative natural frequency;
c. To a reduction of pitch in static or quasi-static conditions, but also to a decrease of the relative natural frequency.

Answer 1

b. To a reduction of pitch in static or quasi-static conditions, but also to an increase of the relative natural frequency;

Question 2

52) In order to decouple of the directional behavior and the squat motion to be possible, there must be verified the following hypothesis:
a. The existence of a symmetry plane ( xz plane);
b. The linearity of the behavior of the spring and damper; instead, the non-linearity of the spring that simulates the tire behavior can be neglected;
c. Linearity of the trigonometric functions of the angles *, , ϑ ϕ ϕ1 and ϕ2.

Answer 2

a. The existence of a symmetry plane ( xz plane);

Question 3

53) The roll axles for two axle vehicles p, q, r, and , and ψ: ϑ ϕ
a. Coincide;
b. Are different for trigonometric functions of small angles ( ) ϑ ϕ ;
c. Are different for trigonometric functions of big angles ( ). ϕ

Answer 3

b. Are different for trigonometric functions of small angles ( ) ϑ ϕ ;

Question 4

54) The power spectral density of a road profile is measured in:
a. m/(cycle/ m);
b. m2/(cycle/ m);
c. m2/ Hz.

Answer 4

a. m/(cycle/ m);
b. m2/(cycle/ m);
c. m2/ Hz.

Question 5

55) Of how much can roll the chassis with respect to the roll center of the axis?
a. Of a big angle;
b. Of a small angle;
c. Depends on the lateral acceleration.

Answer 5

b. Of a small angle;

Question 6

56) Most annoying frequencies for humans:
a. From 1 to 5 Hz;
b. From 4 to 8 Hz;
c. From 40 to 80 Hz.

Answer 6

b. From 4 to 8 Hz;

Question 7

57) The dof of a model with 10 directional dof are:
a. Displacement in y’, yaw rotation, roll, suspension roll;
b. Displacement y, yaw rotation, roll, suspension roll;
c. Displacement y, pitch rotation, roll, suspension roll.

Answer 7

b. Displacement y, yaw rotation, roll, suspension roll

Question 8

58) The roll center of a suspension is defined as:
a. Center of rotation chassis-ground;
b. Center of rotation chassis-wheels;
c. Center of rotation wheels-ground.

Answer 8

a. Center of rotation chassis-ground;

Question 9

59) The amplification factor of a quarter car model at 1 dof tends to infinity, so the exciting frequency
tends to:
a. Infinity;
b. 1;
c. 0.

Answer 9

b. 1;

Question 10

60) The amplification ratio of the acceleration (ratio between the modulus of the acceleration of the sprung mass and the one of the ground displacement) of a quarter car model with one degree of freedom with λ¿ tending to 0 of the excitation frequency tends to:
a. Infinity;
b. 0;
c. 1.

Answer 10

b. 0;

Question 11

61) The amplification ratio of a quarter car model at 1 dof , when the excitation frequency tends to
infinity, tends to:
a. Infinity;
b. 1;
c. 0.

Answer 11

c. 0.

Question 12

62) The value of the damping that characterizes the condition of maximum comfort, with respect to the one that characterizes the optimum handling is:
a. Equal, according to the simplified model, but actually greater;
b. Equal, according to the simplified model, but actually smaller;
c. Equal.

Answer 12

b. Equal, according to the simplified model, but actually smaller;

Question 13

63) The value of the damping extracted from the quarter car model at 2 dof is (with respect to the system at 1 dof , mass ms and rigidity K):
a. Smaller than the critical damping;
b. Equal to the critical damping;
c. Greater than the critical damping.

Answer 13

a. Smaller than the critical damping;

Question 14

64) In a system at 1 dof with ideal dynamic damper (without other damping other than the one of the dynamic damper), if the damping cs is smaller than the optimum value, there is:
a. One resonance peak;
b. Two resonance peaks;
c. No resonance peak.

Answer 14

b. Two resonance peaks;

Question 15

65) In a 4 steering wheel vehicle, the steering of the rear axle is:
a. Discordant at low speed and concordant at high speed;
b. Concordant at low speed and discordant at high speed;
c. Always discordant.

Answer 15

a. Discordant at low speed and concordant at high speed;

Question 16

66) In a quarter car model at 2 dof , if the damping tends to infinity, there is (are): a. 2 peaks of resonance with infinite height;
b. 1 peak of resonance with finite height;
c. 1 peak of resonance with infinite height.

Answer 16

c. 1 peak of resonance with infinite height.

Question 17

67) In an ideal suspension with rigid axle the kinematics must eliminate a number of dof equal to:
a. 4;
b. 5;
c. 6.

Answer 17

a. 4;

Question 18

68) The roll axle is inclined with respect to the horizontal plane of an angle:
a. Zero;
b. Of small value;
c. Whichever.

Answer 18

b. Of small value;

Question 19

69) The interconnection between the front and rear suspension serves to:
a. Reduce the natural frequency of the vertical motions;
b. Adapt independently the natural frequencies of the vertical motions and those of pitching to the design requirements;
c. To adapt independently the natural frequencies of the vertical motions and those of rolling to the design requirements.

Answer 19

b. Adapt independently the natural frequencies of the vertical motions and those of pitching to the design requirements;

Question 20

70) The torque that the transmission shaft exerts over the solid axle:
a. Doesn’t have any effect over the directional behavior because it’s an internal force to the system;
b. Can have an influence, usually small, over the directional behavior that doesn’t depend on the kind of suspension used;
c. Can have an influence, usually small, over the directional behavior because it modifies the relative position between chassis and axle and therefore, as consequence of driving inaccuracies of the suspensions, can lead to variations of the imposed angles at the tires.

Answer 20

c. Can have an influence, usually small, over the directional behavior because it modifies the relative position between chassis and axle and therefore, as consequence of driving inaccuracies of the suspensions, can lead to variations of the imposed angles at the tires.

Question 21

71) The torsional stiffness of the chassis influences:
a. The vehicle comfort;
b. No motion of the vehicle, as a whole (being a 1 dof of deformation, it can’t interact with the
degrees of freedom of a rigid body);
c. The directional behavior.

Answer 21

c. The directional behavior.

Question 22

72) The lateral deformability of the suspension influences:
a. The vehicle comfort;
b. No motion of the vehicle, as a whole (being a 1 dof of deformation, it can’t interact with the
degrees of freedom of a rigid body);
c. The directional behavior.

Answer 22

c. The directional behavior.

Question 23

73) The power spectral density of the acceleration of the sprung mass S a can be obtained from the one of the road profile S h and of the frequency response H through the formula Sa=H2S h . H is:
a. The ratio between the modulus of the acceleration of the sprung mass and the one of the vertical displacement of the foothold;
b. The ratio between the modulus of the displacement of the sprung mass and the one of the vertical displacement of the foothold;
c. The ratio between the modulus of the displacement of the sprung mass and the one of the vertical acceleration of the foothold.

Answer 23

a. The ratio between the modulus of the acceleration of the sprung mass and the one of the vertical displacement of the foothold;

Question 24

74) The flexion at the vehicle’s characteristic plane (horizontal) influences what?
a. The vehicle comfort;
b. The directional behavior (handling);
c. None of the above.

Answer 24

b. The directional behavior (handling);

Question 25

75) The position of the roll axis: a. In general doesn’t depend on the load conditions of the vehicle; b. Is fixed with respect to the ground, but its position with respect to the chassis depends on the load conditions of the vehicle; c. In general depends on the load conditions of the vehicle.

Answer 25

c. In general depends on the load conditions of the vehicle.

Question 26

76) The steering of the rear axle of the trucks is: a. In general concordant; b. In general discordant; c. Depends on the velocity.

Answer 26

b. In general discordant;

Question 27

77) The steering of the rear axle in a 4 steering wheel vehicle must be: a. Discordant at low speed and concordant at high speed (because there are small sideslip angles at high speed); b. Concordant; c. Always discordant.

Answer 27

a. Discordant at low speed and concordant at high speed (because there are small sideslip angles at high speed);

Question 28

78) The optimum damping for a quarter car model at 1 dof is: a. Smaller than the critical damping; b. Equal to the critical damping; c. Greater than the critical damping.

Answer 28

a. Smaller than the critical damping;

Question 29

79) In the directional behavior of the vehicle it’s possible to decouple the motion of the suspensions if it’s done: a. The complete linearization of the model (including tires), and exists a symmetry plane; b. The complete linearization of the model (not including tires), and exists a symmetry plane; c. The complete linearization of the model (not including tires), and exists a symmetry plane, with small yaw angle.

Answer 29

a. The complete linearization of the model (including tires), and exists a symmetry plane;

Question 30

80) At the equation of motion of the suspension of a vehicle schematized through a 10 dof model, the coordinate x is eliminated, remaining only 4 dof : a. This procedure is rigorous and doesn’t allow further approximations; b. This procedure is approximate, but the approximations it introduces are generally acceptable; c. This procedure is approximate, but allows to consider the interaction between x and y directions of the tires.

Answer 30

a. This procedure is rigorous and doesn’t allow further approximations;

Question 31

81) At the equation of motion with respect to the squat motion, the rigidity matrix results non-symmetric. That is due to: a. The fact that the system is damped; b. The fact that the moment of inertia around y axis is not equal to the product of the mass to the distance of the axles to the center of gravity ( mab ); c. The fact that it doesn’t derive completely from conservative forces (there are included aerodynamic - dissipative - forces).

Answer 31

c. The fact that it doesn’t derive completely from conservative forces (there are included aerodynamic - dissipative - forces).

Question 32

82) In suspensions with independent wheels, refers to and z (unique, and not z ϕ 1, z2…): a. For the decoupling; b. For simplification, but the decoupling is not interesting; c. ………

Answer 32

b. For simplification, but the decoupling is not interesting;

Question 33

83) At the study of motions of a system at 10 dof , serve: a. 4 dof (roll, pitch, vertical squats); b. 4dof (pitch, vertical squats from the chassis and from the axles); c. 6 dof (pitch, vertical squats from the chassis and from the 4 wheels).

Answer 33

b. 4dof (pitch, vertical squats from the chassis and from the axles);

Question 34

84) Order at which to consider the characteristic angles: a. Yaw, roll and pitch; b. Roll, pitch and yaw; c. Yaw, pitch and roll.

Answer 34

c. Yaw, pitch and roll.

Question 35

85) In order to decouple the equations of a system with 10 dof : a. It must be taken into account the tire stiffness that allows decoupling but not the linearity; b. It must be taken into account the tire stiffness that doesn’t allow decoupling but allows linearity; c. It must be taken into account the tire stiffness that allows decoupling and linearity;

Answer 35

a. It must be taken into account the tire stiffness that allows decoupling but not the linearity;

Question 36

86) For the system with dynamic damper, if Cs tends to infinity, the frequency tends to which value? a. 0 Hz; b. 1 Hz; c. Infinite.

Answer 36

b. 1 Hz;

Question 37

87) If in the optimization of the handling it is taken into account also the vertical displacements (in order to minimize the effects of the suspensions inaccuracies) in addition to the vertical accelerations (in order to reduce the variations of forces at the ground), the value of the optimum damping coefficient: a. Increases; b. Remains equal; c. Decreases.

Answer 37

Increases;

Question 38

88) A rotating component has its rotation axis parallel to the z axis of the vehicle. The gyroscopic effect: a. Doesn’t influence at all the decoupling between the directional behavior and the squat motion; b. Prevents the decoupling between the directional behavior and the squat motion; c. Has an influence over the decoupling between directional behavior and squat motions that depend on the sense of rotation.

Answer 38

b. Prevents the decoupling between the directional behavior and the squat motion;

Question 39

89) A trailer with one axle with its center of gravity over the axle: a. Doesn’t influence the directional behavior of the truck in stationary conditions (but influences its behavior in transitory conditions); b. Never influences the directional behavior of the truck; c. Always influences the directional behavior of the truck.

Answer 39

a. Doesn’t influence the directional behavior of the truck in stationary conditions (but influences its behavior in transitory conditions);

Question 40

90) A vehicle with 10 dof with two rigid axle suspensions and locked control has how many dof ? a. 10; b. 8; c. 6.

Answer 40

a. 10;

Question 41

91) A vehicle with trailer with one non-steering axle; if the center of gravity of the trailer is over the axle it doesn’t influence the study of the vehicle in stationary conditions. During the transitory comes into play in the directional behavior: a. TheJ r of the trailer; b. The cornering stiffness of the tires of the trailer; c. The weight of the trailer.

Answer 41

a. TheJ r of the trailer;

Question 42

92) The optimum value of the damping through a quarter car model with 2 dof ( μs, K): a. Is greater than the critical damping; b. Is smaller than the critical damping; c. Is equal to the critical damping.

Answer 42

b. Is smaller than the critical damping;