Assignment 4

AIM:

       1. Total number of cycles, Energy error, mass error and simulation time.
       2. Notice the animation of all 5 and describe the animations in brief on the basis of whether the elements are being deleted or cracked.
       3. Plot energies and notice any difference.
       4. Based on all the results, which case would represent the on-field scenario.
       5. Prepare a ppt/docx and list down case by case result and your conclusion as to why the failure happened.

DESCRIPTION:

RUPTURE PLATE:

                          A rupture disk is a device designed to function by the bursting of a pressure-retaining disk. This assembly consists of a thin, circular membrane usually made of metal, plastic, or graphite that is firmly clamped in a disk holder. When the process reaches the bursting pressure of the disk, the disk ruptures and releases the pressure. Rupture disks can be installed alone or in combination with other types of devices. Once blown, rupture disks do not reseat; thus, the entire contents of the upstream process equipment will be vented. Rupture disks are commonly used in series (upstream) with a Relief valve to prevent corrosive fluids from contacting the metal parts of the valve. In addition, this combination is a reclosing system. The burst tolerances of rupture disks are typically about ±5% for set pressures > 40 psig.

PURPOSES OF RUPTURE DISKS:

                                                 A rupture disk is a sensitive relief device designed to rupture at a pre-determined pressure and temperature. It is a means of providing protection for personnel and equipment. As such, it must be a fail-safe device. Rupture disks are used where instantaneous and full opening of a pressure relief device is required. These devices are also utilized where "zero" leak-age is required of a relief device. These devices can also be used in series as "quick opening" valves. It may be used either in primary relief, in secondary relief, in series with a Relief valve, or for other functions like "quick opening" valves.

PRIMARY RELIEF:

                            If used for primary relief, the rupture disk is the only device utilized for pressure relief. As such, it has the advantages of being leak tight, an instantaneous response time, minimum pressure drop, lowest cost, very high re-liability, and minimum maintenance. It has the disadvantage that it must be replaced after each rupture occurrence, and allows venting until system pressure equals downstream pressure.

SECONDARY RELIEF: 

                                 When used in a secondary relief capacity, the rupture disk provides a backup vent to a primary relief device, usually a Relief valve. Its purpose here is usually to provide additional protection against an unlikely but possible major event that would exceed the capacity of the primary relief device.

IN SERIES WITH RELIEF VALVE:

                                                    When used in series with a pressure Relief valve, the rupture disk is usually installed upstream of the valve. The disk will protect the valve from process media that can corrode or plug it. The disk can also act as a seal, preventing any leakage through the valve unless the disk is ruptured. The space between the rupture disk and the pressure Relief valve must have a pressure gauge, try cock, free vent, or suitable telltale indicator. The normal configuration is an excess flow valve in combination with a pressure gauge. This arrangement is to eliminate the possibility of, or facilitate the detection of, a backpressure build up. Because a disk responds to the differential pressure across it, it will not burst at its rated pressure if a back pressure is allowed to exist in this cavity. A low-pressure rupture disk can be used on the downstream side of a Relief valve that discharges into a common manifold to prevent exposure of the valve to process or corrosive media discharging through the common manifold. The space between the Relief valve outlet and the rupture disk must be vented to prevent the accumulation of pressure, which could adversely affect the Relief valve set pressure. An excess flow valve will suffice for this feature.

OTHER FUNCTIONS:

                               Due to the small inertia characteristics of a rupture disk, the opening time, i.e., from a closed and sealed condition to a full open condition, is less than one half of one millisecond (0.0005 sec.). This characteristic allows a rupture disk to function as a "quick opening" valve. Some examples of rupture disks utilized in this manner are: 1) shock tube operations; 2) seismic testing; 3) simulation of large caliber gun discharges; 4) shifting of control mechanisms from a remote location; 5) injection systems for suppression of upsets within storage vessels or systems.

PROCEDURE:

STUDY-1:

               We run the simulation with default material parameters, recommended & default failure properties. Import the rad file Failure_Johnson_0000.rad & run the simulation with default material & shell properties.

When the file is imported cycle runs & looking for energy & mass error.

Energy error - 0.8%

Mass error - 0

Once the simulation is done select the h3d file to check von mises on contour plot with simple method.

Plot the graphs for internal energy, kinetic energy & total energy.

In this case due to heavy loads, plastic strain followed by severe plastic strain & it's finally fails.

STUDY-2:

              We run the simulation with default material parameters, recommended properties & change the values of Ifail_sh=1, Dadv=1 & Ixfem=1 in the failure card. 

Import the rad file Failure_Johnson_0000.rad & run the simulation with default material & shell properties also change the values which has been mentioned above in the failure card.

 

 When the file is imported cycle runs & looking for energy & mass error.

Kinetic Energy error - 4.5%

Mass error - 0

Once the simulation is done select the h3d file to check von mises on contour plot with simple method.

Plot the graphs for internal energy, kinetic energy & total energy.

 

In this case loads will undergo plastic strain followed by severe plastic strain & it fails. Deletion of plate element & crack advancement is observed.

STUDY-3:

              We run the simulation with recommended properties, default material parameters & we delete the Fail_Johnson failure card.

Import the rad file Failure_Johnson_0000.rad & run the simulation with default material & shell properties also delete the Fail_Johnson which has been mentioned above in the failure card.

In this case we are deleting Failure_Johnson as per the study mentioned above.

When the file is imported cycle runs & looking for energy & mass error.

Energy error - 0.8%

Mass error - 0

Once the simulation is done select the h3d file to check von mises on contour plot with simple method.

 Plot the graphs for internal energy, kinetic energy & total energy.

In this case kinetic energy plot indicates elements are deleted once strain rate reached its maximum range.

STUDY-4:

              We run the simulation with recommended properties, default material parameters & remove the value of EPS_p_max in the material card.  Import the rad file Failure_Johnson_0000.rad & run the simulation with default material & shell properties also remove the value of EPS_p_max in the material card.

When the file is imported cycle runs & looking for energy & mass error.

 

Kinetic Energy error - 11%

Mass error - 0

Once the simulation is done select the h3d file to check von mises on contour plot with simple method.

 Plot the graphs for internal energy, kinetic energy & total energy.

 In this case EPS_p_max is deleted so there is no plastic strain hardening. Thus internal energy has exponential growth, so elements are only streched till plastic limit.

STUDY-5:

              We run the simulation with recommended properties, default material parameters & change the card image to M1_ELAST defines an isotropic linear elastic material in the material card.  Import the rad file Failure_Johnson_0000.rad & run the simulation with default material & shell properties also change the value of M1_ELAST in the material card.

When the file is imported cycle runs & looking for energy & mass error.

Kinetic energy error - 0.8%

Mass error - 0 

Once the simulation is done select the h3d file to check von mises on contour plot with simple method.

 

Plot the graphs for internal energy, kinetic energy & total energy.

 

Thus the material is linearly or purely elastic there is no plastic strain. It streches & shape has been changed into original shape, when load is retrieved.

STUDY-6:

               We run the simulation with default material parameters, recommended & default failure properties. Import the rad file Law27_0000.rad & run the simulatiion with default material & shell properties, run it with default parameters.

When the file is imported cycle runs & looking for energy & mass error.

Kinetic energy error - 0.8%

Mass error - 0

Once the simulation is done select the h3d file to check von mises on contour plot with simple method.

 

Plot the graphs for internal energy, kinetic energy & total energy.

Elements gets deleted, when the plastic strain reaches to the lower value, while brittle material is used. 

STUDY-7:

              We run the simulation with default material parameters, recommended & default failure properties. Import the Failure_Johnson_0000.rad & run the simulation with default material & shell properties also change the M36_PLAS_TAB in the material card. Also import the values which has been given. 

When the file is imported cycle runs & looking for energy & mass error.

Kinetic energy error - 1%

Mass energy - 0

Once the simulation is done select the h3d file to check von mises on contour plot with simple method.

 

Plot the graphs for internal energy, kinetic energy & total energy.

Element gets deleted when plastic strain reaches to the lower value. High elongation loads will undergo plastic strain & finally fails. 

COMAPRISON OF ALL THE 7 CASES:

• By comparing all cases that energy errors are obtained i.e; standard values lie between -15% to +5% 
• Mass error on the other hand for all the cases is zero.
• No of cycles & elapsed time depend on the type of the material used in the simulation.
• From all the above cases Law 36 is an isotropic elastoplastic material that indicates user defined functions for the stress strain curve at different rates.

 RESULTS:

• Different material applications is used for performing the experiment with variation of material laws.
• In all cases simution process is done & graphs has been plotted for kinetic, internal & total energy.