Temperature and heat effects on polyethylene behaviour in the presence of imperfections

This paper highlights the changes of polyethylene behaviour during various loading rates as well as the influence of test temperature on the material characteristics. Passive infrared thermography method and a high speed infrared camera were used to observe the temperature changes of the sample surface during the tests. The experimental program was carried out on samples taken from PE80 polyethylene gas pipes with simulated imperfections with bilateral V-notch, U-notch, and central hole. Samples have been tensile tested and the results are correlated with the temperature distribution of the samples surface

Stereometric measurement for assessing structural integrity of welded structures

Ovaj rad predstavlja mobilni sistem u kome su implementirane teorije upravljanja i mašinskog vida u sprezi sa teorijom procene integriteta i veka zavarenih kostrukcija. Tehnički sistem koji je korišćen sastoji se od dve video kamere čijom je upotrebom obezbeđen stereometriski vid, odnosno dobijanje trodimenzionalne slike u realnom vremenu. Prednost ove metode nad ostalima je u bržoj obradi podataka, postizanja veće efikasnosti i sniženje troškova projektovanja.This paper presents a mobile system in which are implemented control theory and machine vision in conjunction with theory of integrity and life assessment of welded structures. The technical system is system with two video cameras, by which is provided stereometric vision, to obtain three - dimensional image in real time. The advantage of this method is the faster data processing, archiving greater efficiency and cost reduction design

Stereometric measurement for assessing structural integrity of welded structures

Ovaj rad predstavlja mobilni sistem u kome su implementirane teorije upravljanja i mašinskog vida u sprezi sa teorijom procene integriteta i veka zavarenih kostrukcija. Tehnički sistem koji je korišćen sastoji se od dve video kamere čijom je upotrebom obezbeđen stereometriski vid, odnosno dobijanje trodimenzionalne slike u realnom vremenu. Prednost ove metode nad ostalima je u bržoj obradi podataka, postizanja veće efikasnosti i sniženje troškova projektovanja.This paper presents a mobile system in which are implemented control theory and machine vision in conjunction with theory of integrity and life assessment of welded structures. The technical system is system with two video cameras, by which is provided stereometric vision, to obtain three - dimensional image in real time. The advantage of this method is the faster data processing, archiving greater efficiency and cost reduction design

The performance of pip-cascade controler in hvac system

Primitive controllers used in the early version for HVAC systems, like the on-off (Bang-Bang) controller, are inefficient, inaccurate, unstable, and suffer from high-level mechanical wear. On the other hand, other controllers like PI and cascade controllers, overcome these disadvantages but when an offset response (inaccurate response) occurs, power consumption will increase. In order to acquire better performance in the central air-conditioning system, PIP-cascade control is investigated in this paper and compared to the traditional PI and PID, in simulation of experimental data. The output of the system is predicted through disturbances. Based on the mathematical model of air-conditioning space, the simulations in this paper have found that the PIP-cascade controller has the capability of self-adapting to system changes and results in faster response and better performance

The performance of pip-cascade controler in hvac system

Primitive controllers used in the early version for HVAC systems, like the on-off (Bang-Bang) controller, are inefficient, inaccurate, unstable, and suffer from high-level mechanical wear. On the other hand, other controllers like PI and cascade controllers, overcome these disadvantages but when an offset response (inaccurate response) occurs, power consumption will increase. In order to acquire better performance in the central air-conditioning system, PIP-cascade control is investigated in this paper and compared to the traditional PI and PID, in simulation of experimental data. The output of the system is predicted through disturbances. Based on the mathematical model of air-conditioning space, the simulations in this paper have found that the PIP-cascade controller has the capability of self-adapting to system changes and results in faster response and better performance

Non-homogeneity effect in the spherical shell by using seth's theory

This paper presents nonlinear deformation behaviour of non-homogeneous spherical shell examined under pressure by using Seth's transition theory. It has been seen that for increased material compressibility in thickness direction, the circumferential stress in the spherical shell reaches maximum at the external surface, but is reverse in the case of a deceasing compressibility in the thickness direction. The spherical shell of non-homogeneous material (non-homogeneity increases radially) is on the safer side of design. Hence, the more use of non-homogeneous material (non-homogeneity increases radially) may be beneficial for manufacturing spherical shells as they provide longer service life than shells of homogeneous material under identical conditions

Non-homogeneity effect in the spherical shell by using seth's theory

This paper presents nonlinear deformation behaviour of non-homogeneous spherical shell examined under pressure by using Seth's transition theory. It has been seen that for increased material compressibility in thickness direction, the circumferential stress in the spherical shell reaches maximum at the external surface, but is reverse in the case of a deceasing compressibility in the thickness direction. The spherical shell of non-homogeneous material (non-homogeneity increases radially) is on the safer side of design. Hence, the more use of non-homogeneous material (non-homogeneity increases radially) may be beneficial for manufacturing spherical shells as they provide longer service life than shells of homogeneous material under identical conditions

Numerical Evaluation of the Elastic Properties of Carbon Fiber Reinforced Composite Material at Elevated and Lowered Temperatures

The effect of elevated and lowered temperatures on the elastic properties of carbon fiber-epoxy composite material was studied using multi-phase unit cell (MPUC) numerical model. Evaluation of the elastic properties of carbon fiber-epoxy composite material is based on the finite element method. Obtained results confirmed that elevated and lowered temperature has noticeable influence on elastic properties of carbon fiber-epoxy composite material. As demonstrated, this fact has considerable influence on accurate evaluation of generated thermal stresses in real laminated composite structures, exposed to extremely high or low operating temperatures

Analytical vs Numerical Calculation of Fatigue Life for Different Welded Joint Regions

This research will show the analytical way of determining the remaining life of a welded joint with a fatigue crack initiated in its heat affected zone. The calculation will be divided into two stages, since the fatigue crack propagated through the heat affected zone, and then through the parent material. The analysis will be related to specimens with different fatigue properties taken into account for both regions. These calculations included a number of models, since different crack lengths were used for the heat affected zone and the parent material. There were three pairs of different HAZ vs PM fatigue crack lengths, always with the assumption that the total crack length is 5 mm, due to measuring range of the used measuring foils. The aim of this analysis was to apply method typically used in fracture mechanics in order to determine the number of cycles in a welded joint with an initiated fatigue crack, depending on a number of parameters. Obtained results were then compared to the results from the numerical analysis for the same cases. While the total number of cycles was mostly unaffected by these changes, some noticeable differences were observed between individual welded joint regions in question, the heat affected zone and the parent material

Analytical vs Numerical Calculation of Fatigue Life for Different Welded Joint Regions

This research will show the analytical way of determining the remaining life of a welded joint with a fatigue crack initiated in its heat affected zone. The calculation will be divided into two stages, since the fatigue crack propagated through the heat affected zone, and then through the parent material. The analysis will be related to specimens with different fatigue properties taken into account for both regions. These calculations included a number of models, since different crack lengths were used for the heat affected zone and the parent material. There were three pairs of different HAZ vs PM fatigue crack lengths, always with the assumption that the total crack length is 5 mm, due to measuring range of the used measuring foils. The aim of this analysis was to apply method typically used in fracture mechanics in order to determine the number of cycles in a welded joint with an initiated fatigue crack, depending on a number of parameters. Obtained results were then compared to the results from the numerical analysis for the same cases. While the total number of cycles was mostly unaffected by these changes, some noticeable differences were observed between individual welded joint regions in question, the heat affected zone and the parent material