42

If you consider only the static forces then indeed the thickness might seem over-engineered. However, engine blocks are not statically loaded. They operate in the range of a few hundred to a few thousand rpm (Revolution Per Minute), so there are dynamic considerations here. Fatigue When materials are subjected to cyclic loading they exhibit a reduction in ...


16

You need to consider that the complete engine block has to withstand the reciprocating forces generated by each of the pistons and con rods moving as well as the rotational forces from the rotating crankshaft. The 1 litre 4 cylinder engine used in the Hillman imp was known for twisting under load especially once it was tuned as it was an aluminium block. One ...


12

It really depends on the problem and what you want to capture. Usually, in classes, it may be beneficial for the students at an initial stage to disregard gravity alltogether in order to simplify the equations of motion. Below are a few scenarios, starting from the most trivial. Horizontal Case In the following mass spring system: There is no point in ...


12

The vibration, loading, and fatigue aspects have already been addressed, but a wide range of operating temperatures is another factor. A typical consumer engine can be deployed in anything from say -50F to 120F (-45C to 50C), and some blocks will crack when operated or even stored at those extremes. An engine operating at those extremes will experience ...


4

No one has mentioned yet that there are structural loads placed on the block by other components. The first that comes to mind are the cylinder heads, and as it (they) are torqued, the block needs to resist distorting due to those loads.


4

The example picture does not show a very solid outter wall; what you see a gasket surface. A closer look will show a lot of variations in thickness, with a lot of ribbs, bulky parts (for mounting, and vibration damping) but also very thin sections, that are just strong enough to contain the water pressure. Vibration and fatique are indeed important factors. (...


4

Vibrations are the manifestation of things occurring at some frequency. This can be one per rev from imbalance (nothing is ever perfectly balanced) in gears spinning, one per tooth from each tooth changing where it presses against another tooth, one per specific tooth if a tooth exhibits an anomaly differentiating it from other teeth, specific interactions ...


3

No. Strobes are useful for what they can do, but they are not substitutes for accelerometers. A strobe can give you a "picture", but it doesn't measure anything except maybe frequency. It doesn't measure amplitude, harmonic content of the vibration, etc. Also a strobe is only useful for amplitudes which are big enough to see. Accelerometers can ...


3

Is stroboscope a useful device to control the translational vibrations? No. A stroboscope, also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a rotating disk with slots or holes or a lamp such as a flashtube which produces brief repetitive flashes of light. ...


3

Most acoustic vibrations of air more or less confined to a given geometry can be explained by two basic models. One is the one-dimensional treatment of the air in a tube, and the other is the lumped-parameter treatment of the air within a volume that has a small hole in its side. The former is called a quarter-wave or half-wave tube, depending on the nature ...


3

The frequency of the sound you're hearing is related to the changing resonant frequency of your bottle based on the frequency/velocity relationship of sound waves v=f*λ Velocity (v) is the speed of sound in air which is nearly constant, typically 343 m/s. The length of the air column in your bottle is the wavelength (λ) of the resonant frequency. So as the ...


2

In the section "The Multiple DOF System" the Comsol document says It has been assumed that the mass matrix normalization of the eigenmodes is used and that the damping matrix can be diagonalized by the eigenmodes. Eigenvectors are assumed to be mass normalized in any mathematical derivation using them, unless somebody wants to be deliberately ...


2

Yes it is, and portable stroboscopes are commonly used in industry to help visualize linear vibrations as well as rotary ones. You will also find it handy to have on hand an oscilloscope and microphone for measuring vibrations because this setup will also furnish you with information on the spectrum of different frequencies present in the system, which is ...


2

This is more of a continuation of the comments. Maybe later with more information it will be converted to a proper answer. Low pass filter frequency response Low pass filters have a specific response with respect to frequency. A typical example for a low pass filter is presented below. In the image above, the cutoff frequency is 1. Notice that the x-axis is ...


2

For a discrete system with $N$ degrees of freedom, the displacement can be expressed as $$ \mathbf{u}(t) = \sum_{i=1}^N \boldsymbol{\Phi}_i \Gamma_i s_i(\omega_i, t) $$ where $\boldsymbol{\Phi}_i$ is the mode shape, $\Gamma_i$ is the participation factor, and $s_i$ is a function of the modal frequency, $\omega_i$. The second derivative of the displacement,...


2

I agree totally with Jonathan R Swift's answer but I will try to give a insight as to why it is not appropriate to use a shock absorber. The main issue is that the excitation frequency of the vibration is not constant. The vibrations frequency will change depending on how fast the car will travel and on the roughness of the road. All things being equal if ...


2

Usually if you can get rid of extra vibration of car seat and be satisfied with the vibration of the car itself you should be happy. For examplev the instrument panel of an airplane is the absolute most critical interface between the pilot and the plane. it is directly mounted on the frame. They would have mounted it on a shock absorber base if it would help....


1

As you know you already had better results with softer compounds. So if you image the solid block as a spring, then you need a spring with a lower coefficient K. So you need to have higher displacement for a given force to follow hooke's law: $$F = - K\cdot x$$ Now, the solid block isn't immediately recognizable as a spring, however you can estimate it as a ...


1

First of all, there will be two deflection equations, because the stiffness is not uniform. I'm getting the impression you somehow tried to use a single equation for the whole beam, which would obviously fail. The basic equation for cantilever beam you posted seems correct. Now for the left part you can use that as is, substituting the total length (L1+L2) ...


1

Springs and dampers are the classic method to reduce vibration, but don't expect the solution to be easy. Vibrations is a 4000 level ME course. If the problem is just the floor, then hanging the bed is probably the easiest option. I would recommend 4 ropes or chains anchored into the ceiling joists above the bed.


1

A number of years ago I was in a similar situation. As kamran says, the entire building is involved. Before going further, I would point out that whether or not you are able to ignore it / whether you even care, is in significant part a product of your own stress level, possibly to do with the actual source of the disturbance, possibly unrelated. Current ...


1

I would try the cheapest way first - sleep on the stacked up mattresses without frame, nor box spring, to increase the effect of damping. A thick wall to wall carpet underneath will provide extra help to block out the noise.


1

Here is an antivibration mount which will probably work, and is cheap: Get you four small inner tubes (as used in wheelbarrows or small garden wagons, hand trucks, etc. and inflate them about half-full of air. Cut you four squares of plywood to the same size as the inner tubes and place one square atop each of the tubes. Lift your bedframe up off the floor ...


1

Apart from the other two valid options (rubber pads and anti-vibration mounts) another (maybe less expensive) option would be to increase the mass which is attached on the bed. effectively you would be creating option (c) in the above diagram. Increasing the mass, (in a simplified model) would decrease the eigenfrequency $\omega_n$. Therefore, (assuming ...


1

I would say it's the entire building, including your ceiling and even the foundation of the building that is vibrating. I have seen even the sidewalk shaking. Remedies can be very elaborate and costly with just a slight improvement. I would try something like this floor barrier in combination with earplugs and maybe eye blinds with rubber pads under your bed ...


1

It's difficult to say what will work in your situation. I think some trial and error might be involved. Constructing a frame and hanging the bed as you suggest could work but I would vibration dampers under each leg of the frame and if possible in each of the hanging ropes. It seems a lot of work though. It might be easier to put some vibration dampers under ...


1

Use this fork: https://github.com/AeroDME/NASTRAN-95 Use gFortan and cmake to build it on windows 10.


1

The following graph shows you the properties of Polypropylene at high strain rates As you see here the modulus increases with increasing displacement rate (its not entirely equal to strain rate but its closely related). The effect is due to this viscous damping. Polymers usually are more strongly affected, in terms of modulus and ultimate tensile strength. ...


1

Let's consider a mass and spring system in a frictionless open channel attached at one end to the channel. so that we can position the channel vertically or horizontally. If we position the channel vertically it will initially deflect by the amount $Y_{initial}= \frac{mg}{k} $ due to gravity. But the gravity is not changing so it can not affect the vibration....


1

I'm not an expert, but that vertical line in the phase is usually when transitioning over a critical rotational velocity of a shaft. This happens when the excitation frequency "transverses" the critical frequency of the shaft. The displacement of the shaft can be derived for an ideal motor (no damping): $$ y = \frac{e\cdot \omega^2}{\omega_n^2 - \...


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