Thermal post-buckling characteristics of clamped skew plates

Thermal post-buckling characteristics of clamped skew plates with restrained edges subjected to planar temperature distributions are studied. The problem is formulated in terms of Von Kármán equations expressed in terms of displacements generalised to include thermal effects. A perturbation method is employed to obtain a linear set of partial differential equations. The solution to this linear set is then obtained by using the Galerkin method. Numerical results are presented for different skew plate configurations for both uniform and two-dimensional temperature distributions. Plots of central deflection, membrane and bending stress distributions are presented and the post-buckling characteristics are discussed in detail.     

Framework for evaluation and selection of the software packages: A hybrid knowledge based system approach

Evaluation and selection of the software packages is complicated and time consuming decision making process. Selection of inappropriate software package can turn out to be costly and adversely affects business processes and functioning of the organization. In this paper we describe (i) generic methodology for software selection, (ii) software evaluation criteria, and (iii) hybrid knowledge based system (HKBS) approach to assist decision makers in evaluation and selection of the software packages. The proposed HKBS approach employs an integrated rule based and case based reasoning techniques. Rule based reasoning is used to capture user needs of the software package and formulate a problem case. Case based reasoning is used to retrieve and compare candidate software packages with the user needs of the package. This paper also evaluates and compares HKBS approach with the widely used existing software evaluation techniques such as analytic hierarchy process (AHP) and weighted scoring method (WSM).     

High-Toughness Ce-TZP/Al2O3 Ceramics with Improved Hardness and Strength

Simulataneous additions of SrO and Al₂O₃ to ZrO₂ (12 mol% CeO₂) lead to the in situ formation of strontium aluminate (SrO · 6Al₂O₃) platelets (∼0.5 μm in width and 5 to 10 μm in length) within the Ce-TZP matrix. These platelet-containing Ce-TZP ceramics have the strength (500 to 700 MPa) and hardness (13 to 14 GPa) of Ce-TZP/Al₂O₃ while maintaining the high toughness (14 to 15 MPa ± m^1/2) of Ce-TZP. Optimum room-temperature properties are obtained at SrO/Al₂O₃ molar ratios between 0.025 and 0.1 for ZrO₂ (12 mol% CeO₂) with starting Al₂O₃ contents ranging between 15 and 60 vol%. The role of various toughening mechanisms is discussed for these composite ceramics.     

Analysis of Frequent Failure of Oil Well Tubings Due to Formation of Longitudinal Slit

In an onshore oil field, many premature tubing failures were observed in wells operating on sucker rod pump. Failures were in the form of longitudinal crack/vertical slit. During last three to four years, the failure frequency had increased and in one well, new tubing vertically cracked in 8 months only. In the internal surface of the tubing, a longitudinal grooving was observed. The shape of the groove resembled the sucker rod and the crack was along the groove. Observation of grooved region under SEM revealed abrasion features typical of mechanical wear. Small corrosion pits were also observed on some portion of grooved region. As the well was vertical, so chance of contact between tubing and sucker rod was low. But tubing was freely suspended in the well, i.e., there was no tubing anchor which made it vulnerable for the buckling. Analytical studies showed that the failed tubing was in buckling region. On comparison of hardness, it was observed that tubing material was softer than the sucker rod. Buckling of the tubing resulted in rubbing of sucker rod against tubing wall due to which tubing had worn out in the form of groove. Wear-oxidation and oxidation-wear of tubing surface at grooved region and corrosive agents of produced water accelerated this material removal process and when the wall thickness of the tubing at groove region reduced to a point where it was not enough to withstand the hoop stresses, a longitudinal crack formed in the grooved region and tubing failed.     

Fingerprint Matching

Fingerprint matching has been successfully used by law enforcement for more than a century. The technology is now finding many other applications such as identity management and access control. The authors describe an automated fingerprint recognition system and identify key challenges and research opportunities in the field.     

Investigation of Cracks Generated in Columbium Alloy (C-103) Sheets During Deep Drawing Operation

Columbium (Niobium) alloy C-103 sheets were formed through deep drawing operations. Two sheets out of a lot of six failed (cracked) during deep drawing. A detailed technical review and microstructural analysis of the failed component was carried out to find out the reasons for cracking. Visual observation of the failed component revealed localized thinning (cup-cone type) at the crack locations. Fractographic observations revealed a predominantly ductile mode of failure. The detailed analysis carried out indicated the failure (crack) is due to nonuniform deformation during first stage deep drawing. This paper provides detail of the failure analysis methodology and present reasons for the failure.