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Fusion welding, which is the most versatile and widely used method of metallurgical bonding, can be troublesome in certain applications like dissimilar metal joining for Ultra High Vacuum requirements. Welding of Stainless Steel to Aluminum by conventional technique is very difficult due to thermal & metallurgical incompatibility. Consequently a number of non-conventional specialized joining techniques were developed. Joining of SS to Al by Electro Magnetic Forming (EMF) method is an effort in this direction. The paper discusses in detail the joining process, joint design and the results achieved.

Buckling is a critical state of stress and deformation, at which a slight disturbance causes a gross additional deformation, or perhaps a total structural failure of the part. Structural behavior of the part beyond 'buckling' is not evident from the normal arguments of static. Buckling failures do not depend on the strength of the material, but are a function of the component dimensions & modulus of elasticity. Therefore, materials with a high strength will buckle just as quickly as low strength ones. If a structure is subject to compressive loads, then a buckling analysis may be necessary. The study presented in this paper is intended to help designers of steel braced barrel vaults by identifying the significant differences in determining which configuration(s) would be best in different conditions of use. The study presented is of parametric type and covers several other important parameters like rise to span ratio, different boundary conditions, such that barrel vault acts as an arch, as a beam or as a shell, The buckling strength of a three different configuration of a double layer braced barrel vaults are presented in this paper for rise/span ratio varying from 0.2-0.7 and having four different types of boundary conditions. Through consideration of these parameters, the paper presents an assessment of the effect of the vault configuration on the overall buckling strength.

Engineering Engineering Physics ANKARA 06100 BESEVL TURKEY Temperature and field dependence of the magnetic behavior of magnetic moments of the rare earth and Mn sublattices of RMn2Ge2, where R is a rare earth element, leads to a variety of interesting magnetic properties. These compounds crytallise in the tetragonal ThCr2Si2 type crystal structure with space group I4/mmm which consist of layers along the c-axis with sequence RGe-Mn-Ge-R. When light rare-earth elements ( Pr, La, Ce or Nd) use in title compounds, the interlayer magnetic coupling in the Mn sublattice is ferromagnetic, whereas it is antiferromagnetic in the case of Gd, Tb or Dy. At low temperatures, the rare earth sublattice also orders and reconfigures the ordering in the Mn sublattice. In this study, crystal structure and magnetic properties of Pr1-xTbxMn2Ge2 compounds were investigated by X-ray diffraction and magnetic measurements. The results of earlier neutron diffraction and Mössbauer studies on samples with x = 0 and x = 1 are also used for interpreting the magnetization data and to give an account on the competing effects between various magnetic structures in the Mn and rare earth sublattices. In low field, we have observed that, temperature dependence of zero field cooled and field cooled magnetizations shows large difference at the Curie temperature of Mn sublattices (TC). This behavior is related to pinnnig of the ferromagnetic components of Mn sublattices and proved that there is an antiferromagnetic ordering of Mn sublattices with Neel temperature TN > TC,which has been observed only by using neutron diffraction techniques. Ingots of several compositions of the Cu(In1-xGax) ~Te5 semiconducting system were prepared by the Bridgman technique in a multi-zone vertical furnace. Xray powder diffraction and optical studies allowed to characterize the fundamental structural aspects and determine the energy band gap Eg. of these materials. The structural study carried out using powder diffraction data collected with a SIEMENS D-5005 diffractomer indicates that a solid solution is formed over the entire range of composition. The parameters a and c of the tetragonal chalcopyrite-related unit cell obtained vary from 6.1639(3) and 12.346(2) Å for x = 0 to 5.9321(8) Å and 11.825(4) Å for x =1, respectively. The variation of the energy band gap with composition is linear, contrary to the quadratic relation of the form Eg = a + bx + cx 2 observed in the Cu(In1-xGax) ~Se5 semiconducting system. This work was supported by grants from CONICIT and CDCHT-ULA. Crystal structure of Sr2YCu2FeO6+δ and Sr2YCu2CoO6+δ has been analyzed using neutron powder diffraction. These compounds consist of nanometer-scale sequence of alternating double CuO2 sheets as those in high-Tc superconductors, and (Fe,Co)Oδ sheet similar to that in the Sr(Fe,Co)O3-δ magnetic compound with brownmillerite-type structure. Sr2YCu2FeO6+δ exhibits superconductivity around 50 K when it is annealed under N2 atmosphere and subsequently under O2 atmosphere, while Sr2YCu2CoO6+δ with the same ...