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Showing 27 results for Defect


Volume 0, Issue 0 (8-2024)
Abstract

Aluminum nano-films are one of the functional elements that have various applications in different fields such as strengthening cement base materials, improving the performance and efficiency of concrete, and enhancing the mechanical and volumetric properties of clay. In this study, the mechanical responses of aluminum nano-film are investigated under uniaxial tensile and compressive tests using the molecular dynamics (MD) method. The initial configuration of the nano-film is constructed based on a 3D aluminum core—alumina shell model that provides a suitable description of surface oxidation in the nano-film. This model is useful to determine the influence of surface oxidation on the mechanical behavior of nan-film. Because of the accuracy and competency, the inter-atomic interactions are evaluated using the EAM+CTI potential, which is a hybrid potential consisting of two components, i.e., EAM and CTI potential, such that it can also take into account the electrostatic interactions between the atoms. After establishing the initial configuration, the energy minimization process is performed on the nano-film, and then its temperature and pressure are adapted to the environmental conditions through the relaxation process. The MD analysis is accomplished by the open-source LAMMPS software, and the visualization of outputs is performed by the open-source OVITO software. The periodic boundary condition is imposed on the lateral sides of the nano-film to eliminate the free surface effect of the atomistic analysis. The tensile and compressive tests are applied to the nano-film in accordance with the experimental tests, and the stress—strain curves are determined. The concept of Virial stress is employed to calculate the stress of the atomic model, which is equivalent to the conventional Cauchy stress in classical mechanics. In order to diminish the dynamic effects, deformation is incrementally applied to the nano-film, such that at each increment, a small strain is gently imposed, then the nano-film is relaxed under the deformed conditions, and finally the stress and strains are evaluated. The numerical simulations are verified by comparing them with experimental data, which demonstrates the acceptable accuracy of the obtained numerical results. The influence of various parameters such as the thickness and the percentages of oxide layers are investigated on the mechanical response and stress-strain curve of aluminum nano-film under the uniaxial tests. It is demonstrated that the thickness of the oxide layer significantly impacts the mechanical behavior, such that the hardness and energy absorption capacity of the nano-film is increased considerably by increasing the percentage of the oxide layer thickness. However, increasing the total thickness of the nano-film leads to a decrease in the Young’s modulus and elastic limit of the specimen. It is because of the decrease in the percentage of oxide layer thickness by increasing the total thickness of the nano-film. Point defects are one of the important imperfections in the crystal structures of atomic configuration that have a significant effect on the mechanical behavior of materials. In order to investigate the influence of point defects, different percentages of voids are generated by randomly omitting some atoms in the nano-film domain. The generated specimens are analyzed under the uniaxial tests, and their mechanical characteristics are evaluated. The numerical simulations demonstrate that the hardness of the nano-film is significantly reduced by increasing the point defects.
 

Volume 7, Issue 0 (0-2007)
Abstract

One of the challenges in non-destructive testing schemes using the ultrasound pulse-echo technique is to identify those defects whose sizes are less than or equal to the detection resolution that is dependent on the width of the ultrasound pulse. Existing methods also require a reference specimen of the same defective material, which may not be available in some cases. We present a new method for detecting and identifying such defects. In the proposed approach, each layer of the test specimen is modeled as a linear time invariant (LTI) filter, and therefore, each defect is characterized by its corresponding impulse response. We use a combination of time gating and system identification techniques to detect and identify the defects, and as such, do not require a reference specimen. To demonstrate the performance of the proposed approach, we tested metallic blocks in which specific defects were impregnated. Results show that the proposed method can detect such defects, does not depend on the test set-up (including the ultrasound transducer), does not require a reference specimen, and is capable of detecting several defects situated in different depth on top of each other

Volume 11, Issue 44 (9-2014)
Abstract


 Mojahed Gholami, PH.D.
Abstract
 
This article, by taking into consideration novel theories on poetry, especially the formalist standpoints, intends to study the efficiency of what is referred to as the defects of eloquence in the contemporary analysis of Farsi poetry. This process has taken place in two generalized and detailed styles. In the generalized process, the issue of dominating element in Russian formalism has been taken into account and interaction has been made between the theories presented on the defects of eloquence in Farsi books. Also, the shortcomings of eloquence up until the end of period of promotion of Hindi styles have been classified and researched in the three domains of compatibility, lack of compatibility and regression. The analysis of this subject leads us to conclude that in the era of compatibility, concurrent with the development of Khorasani style, the views presented on the defects of poems were in line with Farsi poetry. However, this rate of compatibility gradually declined. In the incompatibility era, which was concurrent with the  promotion of Hindi style; the social, literary, and aesthetic needs of Farsi language wiped out the originality of the analysis of contemporary poetry in based on consideration of defects of traditional eloquence.
In the detailed approach, the views of formalists on establishment of unity in language via reduction and addition of a number of norms seem inefficient in identification of defects of eloquence. Based on the analysis of this topic, it was concluded that in the formalist approach and in dealing with modern poetry, the cases taken into consideration as the defects of poetry actually distinguish literary language from ordinary language and ultimately lead to creation of poems.
 

Volume 12, Issue 3 (10-2008)
Abstract

In mutual obligations, the necessity of simultaneous performing of obligation and withholding performance with refusal of the other party has been approved as two interdependent rules in Iranian law and the majority of European countries. What the present essay engaged in is that if one of the counter creditor pioneers carries out the partial of defective performance, what would be the effect of this case on the right of lien of the other party. After pondering and criticizing the different views about this case, the authors came to this conclusion that in the hypothesis of the problem in some cases and considering some conditions in the right of lien, the other party may not withhold his own performance to the same proportion from the obligation that is performed.
Roham Rafiee, Reza Pourazizi,
Volume 13, Issue 13 (3-2014)
Abstract

The aim of this study is to investigate the influence of structural defects on the mechanical properties of single-walled carbon nanotubes. During the growth process and functionalization of carbon nanotubes (CNTs), the Carbon-Carbon bonds in their nano-structure are broken. To evaluate the influence of this defect on the Young’s modulus of CNT, the number of broken C-C bonds, distribution and their arrangements in the nano-structure of CNT are all treated as random parameters. In this study, the finite element model of the CNT is built using nanoscale continuum mechanics approach and then structural defects are applied randomly. The Young's modulus of two defect types, known as Stone - Wales and Vacancy are investigated. The results reveal that the influence of Stone – Wales defect on the Young’s modulus of CNT is much less than that of Vacancy one. Moreover, a linear decrease in Young's modulus with respect to the increase in defect density is observed. In contrast to the available researchers in open literature, three parameters consisting of the number, distribution and arrangement of defects are modeled on the basis of full stochastic simulation.

Volume 14, Issue 4 (10-2023)
Abstract

Among derivational outputs, we come across derivates with no symmetry between their form and meaning, and their analysis is problematic according to morpheme-based approaches. In this research, such asymmetries in Persian verbal derivatives within the framework of theories such as Paradigm Function Morphology by Stump (2001) and Stewart and Stump (2007), are studied. This study seeks to answer the question of how the theory of Paradigm Function Morphology, by using the theoretical device of paradigm, analyzes and explains Persian asymmetric verbal derivatives of 66 verbs collected  from Sokhan comprehensive dictionary. Analysis of Persian asymmetric data in terms of paradigmatic approach showed applying the paradigm function (as a realizational rule) to the lexical root/stem of a verb and morphosemantics properties pair in one cell of verb paradigm can determine the form of a derivative. Also, the assumption of the separation of morphological dimension and semantic dimension in the paradigmatic organization of a lexeme makes the phenomena of suppletion, deponency, defectiveness and syncretismpossible and  justified. So, the asymmetry between form and meaning will no longer be a problem. All verbal derivatives can be analyzed and explained in the same way, whether with or without symmetry between their form and meaning. As a result, a more uniform, general and economical analysis is provided, and there is no need to propose secondary solutions such as zero morpehme, zero derivation and allomorphy which all arise from the assumption of a one-to-one corresondence between the form and meaning of the components of derivatives in morpheme-based approaches.

1. Introduction
The need to study derivational paradigm that display an organized set of cells derived from a lexeme containing morphosemantic properties (such as action noun, agent, etc.), due to gaps and the asymmetry that occurs in the relationship between the form and the meaning of the morphemes in the derivation, is one of the reasons that led to the expansion of the lexeme-based and paradigmatic approaches in the domain of words. Therefore, in some morphological theories, including the theory of paradigm function morphology, morphological analysis is not based on a one-to-one relationship between the form of words and their morphosyntactic or morphosemantics properties. In Stump’s paradigm function morphology theory  (2001) and Stewart and Stump (2007), this asymmetry between form and meaning, which is associated with the occurrence of the morphological phenomena of suppletion, deponency, defectiveness and syncretism in inflection and word formation, is analyzed and explained with the help of the paradigmatic approach and relying on the concept of the lexeme. In this regard, the explanation of Persian asymmetrical verbal derivatives in the framework of the paradigmatic approach is one of the necessities of this research. So, the analysis of Persian derivation based on the paradigmatic approach is conducted in order to find out how some challenges of explaining a number of Persian verbal derivatives with no one-to-one formal and semantic correspondence can be met. Specifically, this research seeks to answer the following question:
1- How does paradigmatic approach analyze and explain the asymmetry of form and meaning of Persian verbal derivatives  regarding the phenomena of suppletion, deponency, defectiveness and syncretism?

2. Literature Review
Irregular morphological phenomena have always attracted the attention of linguists and an answer has been tried to express these irregularities. Within the framework of paradigmatic approach, by considering the word as the unit of analysis, one-to-many or many-to-one correspondences can be better explained. In the present research, these morphological irregularities in Persian are explained by means of paradigmatic functions. This research is  one of the new researches that deals with these morphological irregularities in Persian within the framework of Stump's (2001) theory of paradigm function morphology. In this section, we will introduce a number of researches related to the topic of this research, which have been carried out based on lexeme-based and paradigmatic approaches. Ghatreh (2013) examines inflectional and derivational paradigm ,and by presenting and analyzing examples of derivatives in the framework of paradigmatic approach, states that paradigm has an important role in the uniform analysis of inflection and derivation. Sarahi (2015) gives many examples of asymmetric morphological phenomena that can be explained by both morpheme-based and lexeme-based approaches. According to the generative approach of Halle (1973) and Aronoff (1976), she examines the asymmetric cases in Persian and concludes although the lexeme-based approach seems to be better, compared to the morpheme-based approach, it does not fully match the Persian vocabulary system. Shaghaghi and Mirzaei (2014) studies inflectional paradigms, and by presenting Corbett's (2007) classifications of canonical types, they have introduced deponency and syncretism as violations of canonical inflection in Persian. Arkan (2017) ,in the framework of the lexeme-based approach, examines the stems related to the verb and calls them "morphological stems" that have a separationist concept and the existence of different morphological stems belonging to the same verb is a valid reason for showing the lack of one-to-one correspondence between form and meaning.
According to Booij's definition (2005: 129 and 143), in syncretism, the different cells of verb paradigm are filled with the same phonological form and the suppletive form occurs when two or more grammatical forms have the same word form. Like Stump (2001), he considers the supletive forms require the idea of ​​paradigm in the morphology of language and believes that the suppletive form highlights the importance of paradigm, because it shows that the reason why the word forms of paradigm belong to each other is not always because they are phonologically similar, but it is because they form the paradigm cells of the same lexeme. Bonami and Stump (2016:490) state that the lack of correspondence between form and meaning leads to phenomena such as deponency and suppletion, which can be a motivation for the expansion of the theory in which the content paradigm of a lexexme is different from  its formal paradigm. Hippisley and Stump (2016: 2-3) in the preliminary discussion about the correspondence of form and content, mention the phenomena of syncretism, deponency, defectiveness and null morphology violate the existence of a one-to-one relationship between form and content. The above researches mostly have explained inflectional morphology in terms of paradigms, but previously Stump (1991) has concluded that there is no objection to the notion of a derivational paradigm, or to the use of paradigm functions in resolving morphosemantic mismatches in the domain of derivational morphology. Also the notion of derivational paradigm has been proposed by Štekauer (2014) in attaching affixes to the root of a lexeme.

3. Methodology
The research method is basically qualitative and by using descriptive-analytical method, the verbal derivatives (derived from 66 frequently used Persian intransitive and transitive verbs of the modern Persian language selected from Sokhan comprehensive dictionary (eight volumes), have been described, analzed and explained. Specially purposefully, verbs with suppletive and irregular stems such as DIDAN “to see”, SUXTAN “to burn”, PEYVASTAN “to join" have been selected to explain more asymmetric derivative forms in the data. Importantly, the theoretical framework of Paradigm Function Morphology(Stump,2001), is used to find out how  the Persian irregular morphological phenomena is described and explained.

4. Results
In this research, 66 verbal paradigm were examined, of which 20 were intransitive verbs and 46 were transitive verbs. Out of a total of 722 derived words (from 66 verbs), 510 cases were the derived forms of transitive verbs and 212 cases were the derived forms of intransitive verbs. In sum, 490 asymmetric morphological phenomena were identified. 145 morphological phenomena were related to intransitive verbs, which included 63 cases of suppletion, 59 cases of syncretism, 13 cases of deponency, and 10 cases of defectiveness. From the total of 345 cases of morphological phenomena in the derivatives of  transitive verbs, 232 cases were supletive, 90 cases were syncretic, 14 cases were related to defectiveness, and 9 cases were related to deponency. In both types of verbs, suppletion and  syncretism  were  observed  in the largest number of data. The phenomena of deponency and defectiveness showed almost similar statistics in transitive and transitive verbs.

5. Discussion
The asymmetry between form (formal paradigm) and content (content paradigm) of Persian asymmetric verbal derivatives, regarding the above phenomena, has been examined from the theoretical standpoints of Stump (2001) and Stewart and Stump (2007). Here, the lexeme of verb(infinitive form) is the base of the content paradigm and the verbal root (present / past stem) is the base of the formal paradigm.The analysis of verbal Persian derivatives based on these theoretical standpoints, emphasizing paradigmatic functions, showed that all formal regular and irregular verbal derived words could be accomodated in the paradigmatic organization of a verb lexeme if we explain them by applying the paradigm function to  the pair of the Persian verbal stem and morphosemantic features in each paradigm cell, whether they are symmetrical or asymmetrical. Following this, the final deivational output can be realized and it represents a specific cell in a verb paradigm. So, what is important is not the internal components of a cell,  but the final derived product as a whole entity is important, during formation of which different regular and above irregular morphological phenomena may occur.

6. Conclusion
In the analysis of Persian verbal derivatives based on paradigmatic approach, since paradigm function is responsible for the formation of these derivatives, the form of these derivatives is determined independently of their meaning. The final deivational output represents a specific cell in a verb paradigm and its meaning is determined by means of a separate content paradigm. So, what is important is not the internal components of a cell, but the final derived product as a whole entity is important which represents a cell. Therefore, the formal irregularities in these derivatives relate to the morphological dimension, being different from the semantic dimension.  As a result of assuming the above independent paradigms, one-to-one correspondence between form and meaning of these derivatives is not expected for all cases. So, there is no need to propose secondary solutions such as zero morpehme, zero derivation, allomorphy which all arise from the assumption of a one-to-one corresondence between the form and meaning of the components of derivatives in morpheme-based approaches. Thus, the proposed hypothesis about the separation between formal paradigm and content paradigm can  account for  the asymmetry of their form- meaning relation .
In addition, using theoretical device of paradigm, all derivatives of a verb are explicitly and simultaneously shown to be related and belonging to a verb lexeme as their common focal point in Persian verb paradigm. Assuming  paradaigm organization of Persian verb lexeme results in representing explicitly all filled and empty cells of a verb paradigm (due to defetiveness and deponency), syncretic and suppletive cases  along with regular ones in the derivational paradigm of the Persian verb. As a result,  paradigmatic approach in the analysis of verbal derivatives is more explicit, transparent and general compared to other  morphological approaches

 

Volume 15, Issue 3 (12-2011)
Abstract

            Under Article 50 of the CISG, if the seller delivers a good that does not conform with the contract, the buyer may reduce the price in the same proportion as the value that the goods actually delivered had at the time of the delivery bears to the value that conforming goods would have had at that time. In this case, the buyer acts unilaterally and is not subject to his/her resort to the court and substantiating the lack of conformation before it, although, in any case, the convention provides remedy for the buyer resorting to an undue option. In some cases, in Imamia Jurisprudence and Iran Law, as where there is the claim for some portion of the object of sale belonging to the other and the buyer may be able based on option in sales unfulfilled in part to get some portion of the price and, in some places due to defect in the object of the sale, may cancel the sale or keep it at the price of getting compensation; they all can be legally considered as instances of price reduction. This paper attempts to compare the instances of price reduction in the 1890 Convention, Imamia Jurisprudence and Iran Law, and while putting the concept of price reduction in the Convention, examines its similarities and differences with the ones in Imamia Jurisprudence and Iran Law. In the end, it is discussed whether this option can be possibly applied as a rule in other transactions or not.      
Sadegh Sadeghzadeh, Navid Rezapour,
Volume 16, Issue 1 (3-2016)
Abstract

In this paper, efficiency of defected graphene nano ribbon incorporating with additional nanoparticles on mass detection operations is studied via the Reverse Non Equilibrium Molecular Dynamics (RNEMD) method. Thermal conductivity management of this structure is challenging because of imposed losses in electrical conductivity and any procedure could manage the thermal conductivity of graphene will be useful. In this paper it is observed that on the mass detection operation, due to the porosity generation in the nano ribbon surface or even creation of external nanoparticles, thermal properties of graphene change considerably. This should be noted in calibration of graphene based mass sensors. In summary, results show that the graphene’s thermal conductivity would reduce by increasing the concentration of nanoparticles and thermal conductivity of graphene is higher when porosities and impurities are at the edges. This indicates that the location of vacancies and nanoparticles influences the thermal conductivity. For a better thermal management with the help of nanoparticles, wither respect to the porosities, addition of nanoparticles decrease the thermal conductivity more and more. By increasing the cavity’s diameter from 0.5nm to 4.4nm in a specific single layer graphene, thermal conductivity was reduced from 67 W/mk to 1.43 W/mk.
Yaghoub Dadgar Asl, Mohammad Morad Sheikhi, Ali Pourkamali Anaraki, Vali Ollah Panahizadeh Rahimloo, Mohammad Hosseinpour Gollo,
Volume 16, Issue 5 (7-2016)
Abstract

Today, with the development of technology, industries such as automotive and construction require products with variable cross section. Multiplicity of steps, dimensional limitation and high production costs of the components caused flexible roll forming process used to produce these products. One of the main defects in this process is the fracture phenomenon. The fracture is observed on the bending edges at transition zone that sheet thickness is large compared to the bending radius. In this research the fracture phenomenon is investigated on flexible roll forming process of channel section using ductile fracture criteria. For this purpose finite element simulation of the process using Abaqus software is done. The fracture defect in this process is investigated using six ductile fracture criteria by developing a subroutine. Experimental tests are performed on 27 specimens precut sheet of AL6061-T6, using flexible roll forming machine built in Shahid Rajaee University. By comparing simulation results with experimental results, numerical results were validated. In addition, by comparing the results of ductile fracture criteria with experimental results, the Argon ductile fracture criteria, was chosen as the most appropriate criterion to predict fracture. Also the effects of parameters as sheet thickness, bending radius and bending angle on fracture with argon selected criterion is studied.
Vahid Zal, Hassan Moslemi Naeini, Ahmad Reza Bahramian, Javad Shahbazi Karami,
Volume 16, Issue 9 (11-2016)
Abstract

Due to the polar functional groups of PVC thermoplastic and its good adhesiveness to the metals, production and roll forming of PVC/ aluminuim/ glass fiber FMLs were investigated in this research. At the first, flexural strength and bonding quality between PVC matrix and aluminuim layer in the FMLs were studied by doing three point bending tests according to ASTM D790 standard. In the following, FMLs with dimension of 12×80 cm and two layups including [0/90, 0/90, Al]s and [45/-45, 45/-45, Al]s were produced using film stacking and hot pressing procedure. The FMLs were rollformed into 30, 45 and 60º channel section profiles at 160ᵒC using a single stand rollforming process and geometrical decects including profile bowing, edge wrinkling, spring back and also aluminuim/composite layers delamination of the resulted profiles were evaluated. The FMLs also were roll formed into 86º channel section profiles using a multi stand roll forming process and the effects of multi stand roll forming on the defects stacking were evaluated. Finally, it was concluded that more than 45º bend angle increase in a rollforming stand results in composite/ aluminum delamination. Also, placement of the reinforcing fibers in the longitudinal direction of the profiles reduces the profile bowing and edge wrinkling defects significantly.
Mohammad Ali Rasouli, Aboozar Taherizadeh, Mahmood Farzin, Amir Abdolah, Mohammad Reza Niroomand,
Volume 16, Issue 12 (2-2017)
Abstract

Tube spinning or flow forming process is used for manufacturing of seamless tubes widely put into service in advanced industries. The ideal flow for materials entering the deformation zone in this process is extrusion-type flow in axial direction. Very localized deformation zone which is confined by outer materials and forming tools is very important aspect of this process. Therefore, development of defects during the deformation process with undesirable flow of materials can be easily occurred. The main reason of undesirable flow of materials is choosing inappropriate process parameters which results in arising various geometrical and dimensional defects. In this paper, the effects of process parameters on formation and growth of different defects and their correlations with material flow and forming forces in tube spinning of AA6061 was investigated by using design of experiment (DOE) method. The results of experiments show that by applying the optimized values of reduction and feed rate per revolution, these defects can be controlled. Also, by comparing the experimentally measured and theoretically calculated forming forces it can be shown that the larger the deviation of measured forces from calculated ones gets the more severe formation of defects and undesirable materials flow becomes.

Volume 17, Issue 1 (5-2013)
Abstract

   Consumer protection is very important for the today society. This theory aim to make a legal framework to protect & guarantee the consumer's rights like having safe goods & services right, having information right, choice right, etc. Unfortunately there are not any special rules and provisions in this respect in Iranian law. But the Iranian judges, in their cases, verdict by interpretation of the present law and take help by comparing the Iranian law and regulations with the law and jurisprudence of other same legal systems, like French law. This article compares the conditions and possibility of creating security obligation in Iran and France legal systems. This paper wants to consider the ability of Iranian system to protect the consumer´s rights.   .                        
* Corresponding Author’s E-mail: rkhoshnoodi@yahoo.com
Zahra Azizi, Heshmatollah Haghighat,
Volume 17, Issue 11 (1-2018)
Abstract

This paper attempts to predict the occurrence of central bursting defects in the plane strain extrusion process using upper bound method. For this purpose, the material under deformation is divided into three deformation zones. These deformation zones are separated from each other by the shear boundaries as the exponential functions. Then, an admissible velocity field, including the radial and the angular velocity components are developed for each deformation zone. Strain rates components are determined and mathematical relationships for internal, shear and friction powers are obtained. For a given process conditions, the total power toward geometrical shape of shear boundaries entrance and existence is optimized. Intersection position of the entrance and existence shear boundaries of deformation zone on centerline represents the occurrence of central bursting defects. The effect of process parameters, including semi die angle, reduction in area and friction factor on the defects and the extrusion force are investigated. The analysis results with the FEM simulation (Deform software) and the results of the published papers are compared. The results showed that increase of friction factor and increase the reduction in area decreases the probability of central bursting defects.
Mojtaba Darroudi, Farshad Kowsary,
Volume 18, Issue 4 (8-2018)
Abstract

Detection of defects in the internal surfaces of pipes due to the inherent feature of these surfaces which is inaccessibility is always a troublesome process. In this study, a novel method has been designed for detection of defect locations on the internal surfaces of pipes and accurate estimation of defect geometrical parameters such as length and average material loss depth. The way that this method works is that a band heater is located on the external surface of the pipe in inspection segment, and specified heat flux is applied to this surface for a short time, and the temperature of these sensors located on rear of the band heater is measured during and after of applying thermal heat flux. The local temperature rise on the section of the external surface of the pipe indicates a defect on its internal surface. In this case, a defect with unknown parameters is supposed on the internal surface of the pipe, and by using the inverse heat conduction method, an iterative numerical simulation procedure continues until the unknown geometrical parameters of defects are estimated in a way to minimize the difference between the measured and simulated temperature in the location of sensors.
Mohammad Reza Pakmanesh, Morteza Shamanian, Saeid Asghari,
Volume 18, Issue 5 (9-2018)
Abstract

In the present study, the effect of parameters of autogenous pulsed Nd: YAG laser welding process on the lap joint of a 316L stainless steel foil with a thickness of 100 µm to be used as bipolar plates of polymeric fuel cell was investigated. For this purpose, the statistical tools, the analysis of variance and the various diagrams were used to analyze the data by response surface methodology. The peak power (130 to 650 W), pulse durability (1.5 to 3.5 ms), and welding frequency (14 to 18 Hz) were considered as input parameters. The mentioned statistical method was able to predict the effect of welding parameters by developing second-order polynomials, so that the total error including the repeatability error and the lack of fit error for shear strength model, weld undercut model, and weld underfill model obtained 2, 8 and 3, respectively. The defects of weld undercut and lack of penetration were identified as most important factors affecting the shear strength. The laser power is as the main parameter in this process and the impact of it on the shear strength of the weld, the weld undercut and the weld underfill is calculated 64, 62 and 66%, respectively. Finally, the maximum shear strength with the value of 522 MPa is achieved at a peak power of 260 W, pulsed duration of 3 ms and welding frequency of 17 Hz. In this case, the weld undercut is determined as 3 micrometers.
Ali Habibpour-Ledari, Farhang Honarvar,
Volume 18, Issue 5 (9-2018)
Abstract

The 2D position of a defect as well as its through-thickness length can be measured by ultrasonic time-of-flight diffraction technique (TOFD). By considering the methods used for detecting and positioning a target in radar, acoustic and sonar systems, an algorithm was developed for 3D positioning of defects in TOFD measurements. In this algorithm, the unknown parameter to be determined is the time difference of arrival (TDOA). While the developed algorithm is sufficiently fast, it suffers from various errors affecting the TDOA. The sensitivity of TDOA to errors is more noticeable when the distance between the receivers and the midplane (a plane with a minimum distance from the receivers) is small. This problem cannot be easily resolved when the receivers are coplanar. In this paper, using a closed form solution, a new algorithm is proposed for solving this problem. In this algorithm, by considering hypothetical locations for receivers, both the target (defect) and the positions of receivers are simultaneously verified. These hypothetical positions are obtained in such a way that their distances from the midplane is within acceptable limits. To validate the algorithm, it is used for determining the position of an artificial defect in a carbon steel block. The results prove that the algorithm is accurate and can be used in case of 3D TOFD measurements in which the receivers are usually coplanar.
Mehrdad Honarmand, Mehran Moradi,
Volume 18, Issue 7 (11-2018)
Abstract

For the first time in this paper, by using semi-analytical scaled boundary finite element method (SBFM), a perfect nano garphene sheet or defected ones were simulated and their mechanical behavior had been investigated. In this analysis, the atomic carbon bonds were modeled by simple bar elements with circular cross- sections and then the scaled boundary finite element relations were formulated based on the geometry of the model. The obtained results from SBFM were compared to those obtained from molecular dynamic method which showed that the SBFM can be used as a continuum mechanics model with high accuracy in mechanical analysis of both perfect and defected nano graphene sheets. Existence of structural defects in nano grapheme sheets decrease the strength as well as fracture strain in a considerable manner. It can be noted that in a defected nano grapheme sheet, the fracture stress decreases more than 34% while fracture strain decreases more than 50%. In the cases that instead of using bar elements, whole area is considered as a continuum sheet and in order to obtain a similar geometry to those problems have bar elements, no material zone be modeled by zero elastic properties, the results show considerable errors.

Volume 19, Issue 3 (12-2015)
Abstract

Today complex products enter the market that their use requires compliance with the rules and guidelines that must be provided to the buyer. On the other hand, there are many products in the market that are poor, in terms of safety and quality standards, and not only have financial damage to the consumers but also may endanger their lives. Even the standard products may be inherently dangerous or have dangerous side effects. Under this situation, consumers need the essential information for correct use of the property and purchased goods. Vendors and manufacturers are obliged to provide information and guidance on how to use the product and inform the consumers about the defects that  they should know. This obligation is taken into consideration in many countries, including the Iranian law and English law. Although the parties do not have to repeat all the information and professional secrets to another in the Iranian and English law, and duty to inform the other is limited to the information contained in the decision to enter into a contract, it is not permissible to hide it.
 We can provide information about the scope on the following:
A) INFORMATION about the defects of goods;
B) warnings about the potential dangers of goods;
C) instructions for the better use of the goods; and
D) the technical information relating to the characteristics of the goods
F. Ghodusi Borujeni , H. Jalalifar, S. Jafari, A. Rafati,
Volume 19, Issue 12 (12-2019)
Abstract

Casing collapse is major problem of the oil fields which causes increase of costs to oil companies. This problem can be seen not only at drilling time in some formations but also after the completion and production may cause problems. exact prediction of collapse pressure is a very important factor in the casing design. Casing Collapse generaliy is a function of the geomechanical properties of the formation and the properties of the solid mechanics of the casing. One of the properties of solid mechanics that affects the testing of the collapse can be the ovality of the casing and the difference in the thickness of the casing and the existence of residual stress during the construction of the casing. In this paper, using numerical methods, the effect of each of the above-mentioned solid mechanics parameters and formation creep on the collapse of the casing  has been investigated. The results of this study indicate that pipe defects, such as casing ovality, eccentricity and the presence of residual stress, reduce the strength of the casing.
This reduces the resistance to the extent that the casing at the time of installation due to high plastic strain will collapse and also it was found that the pipe imperfections is more effective than rock salt creep in casing collapse.
 


Volume 20, Issue 3 (11-2016)
Abstract

Indemnity clause due to its importance and being applicable in industrial contracts, in specially oil and gas contracts have a significant role.  According to researches, this clause was firstly incorporated in English marine merchant transportation contracts, which has been gradually recognized in England legal system and courts and other countries; legal systems. Because there is no adequate researche about the comparison of indemnity clause features in Common Law and Civil Law, specially Iran law (or Islamic law), it was necessary to study about.
Contractual terms do not always doesn’t explicitly imply an obligation to-the contract party, so there are some terms implying the discharge of-liability from one party and increasing the other party’s liabilities, the clause which is named indemnity clause, has created some disputes about this scope in judicial decisions. Because of this, negotiations on indemnity clause is so time consuming and controversial.

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