Grid sensitivity capability for large scale structures

The considerations and the resultant approach used to implement design sensitivity capability for grids into a large scale, general purpose finite element system (MSC/NASTRAN) are presented. The design variables are grid perturbations with a rather general linking capability. Moreover, shape and sizing variables may be linked together. The design is general enough to facilitate geometric modeling techniques for generating design variable linking schemes in an easy and straightforward manner. Test cases have been run and validated by comparison with the overall finite difference method. The linking of a design sensitivity capability for shape variables in MSC/NASTRAN with an optimizer would give designers a powerful, automated tool to carry out practical optimization design of real life, complicated structures

Influence of matrix characteristics on fracture toughness of high volume fraction Al<SUB>2</SUB>O<SUB>3</SUB>/Al-AlN composites

The role of matrix microstructure on the fracture of Al-alloy composites with 60 vol% alumina particulates was studied. The matrix composition and microstructure were systematically varied by changing the infiltration temperature and heat treatment. Characterization was carried out by a combination of metallography, hardness measurements, and fracture studies conducted on compact tension specimens to study the fracture toughness and crack growth in the composites. The composites showed a rise in crack resistance with crack extension (R curves) due to bridges of intact matrix ligaments formed in the crack wake. The steady-state or plateau toughness reached upon stable crack growth was observed to be more sensitive to the process temperature rather than to the heat treatment. Fracture in the composites was predominantly by particle fracture, extensive deformation, and void nucleation in the matrix. Void nucleation occurred in the matrix in the as-solutionized and peak-aged conditions and preferentially near the interface in the underaged and overaged conditions. Micromechanical models based on crack bridging by intact ductile ligaments were modified by a plastic constraint factor from estimates of the plastic zone formed under indentations, and are shown to be adequate in predicting the steady-state toughness of the composite

The diffraction of light by high frequency sound waves. Part III. Doppler effect and coherence phenomena

The theory developed in part I of this series of papers has been developed in this paper to find the Doppler effects in the diffraction components of light produced by the passage of light through a medium containing (1) a progressive supersonic wave and (2) a standing supersonic wave. (1) In the case of the former the theory shows that the nth order which is inclined at an angle sin-1 (-n&#955;/&#955;&#8727;) to the direction of the propagation of the incident light has the frequency &#957;-n&#957;&#8727; where &#957; is the frequency of light, &#957;&#8727; is the frequency of sound and n is a positive or negative integer and that the nth order has the relative intensity J2n(2&#960;&#956;L/&#955;) where &#956; is the maximum variation of the refractive index, L is the distance between the faces of the cell of incidence and emergence and &#955; is the wavelength of light. (2) In the case of a standing supersonic wave; the diffraction orders could be classed into two groups, one containing the even orders and the other odd orders; any even order, say 2n, contains radiations with frequencies &#957;&#177;2r&#957;&#8727; where r is an integer including zero, the relative intensity of the &#957;&#177;2r&#957;&#8727; sub-component being J2n-r(&#960;&#956;L/&#955;) J2n+r(&#960;&#956;L/&#955;); and odd order, say 2n+1, contains radiations with frequencies &#957; &#177; 2r+1&#x0305;&#957;&#8727;, the relative intensity of the &#957; &#177; 2r+1&#x0305;&#957;&#8727; sub-component being J2n-r , (&#960;&#956;L/&#955;) J2n+r+1(&#960;&#956;L/&#955;). These results satisfactorily interpret the recent results of Bar that any two odd orders or even ones partly cohere while an odd one and an even one are incoherent

Isolation of Machine Foundations by Barriers

Experimental investigation has been carried out to study the effects due to isolation of foundations subjected to vertical vibration on the displacement amplitude. Tests were conducted on an embedded footing of contact area 45 x 45cm. with different embedments and some on the surface of natural ground. Three isolation barriers viz. air gap, saw dust and sand of various depths were used. From the results of the investigation it was found that an open trench (air gap) around the foundation reduces the displacement amplitude around the footing considerably to an extent of about 75%. Saw dust as a barrier, although not as good as air gap, performs better when compared to sand. The coefficient of attenuation is not a constant for a soil medium but varies with static and dynamic loads. The resonant frequency decreases and resonant amplitude increases by providing isolating barriers

The diffraction of light by sound waves of high frequency. Part II

The theory of the diffraction of light by sound waves of high frequency developed in our earlier paper is extended to the case when the light beam is incident at an angle to the sound wave-fronts, both from a geometrical point of view and an analytical one. It is found that the maxima of intensity of the diffracted light occur in directions which make definite angles, denoted by &#952;, with the direction of the incident light given by sin(&#952;+&#934;) - sin &#934; = &#177;[(n&#955;)/(&#955;&#8727; )], n (an integer) &#8805; 0 where &#955; and &#955;&#8727; are the wave-lengths of the incident light and the sound waves in the medium. The relative intensity of the mth order to the nth order is given by Jm2( &#957;0 sec&#934;[(sint)/t] ) / Jn2 ( &#957;0 sec&#934;[(sint)/(t)]) where &#957;0=2&#960;&#956;L /&#955;,t=&#960;L tan&#934;/&#955;&#8727;, &#934; is the inclination of the incident beam of light to the sound waves, &#956; is the maximum variation of the refractive index in the medium when the sound waves are present and L sec&#934; is the distance of the light path in the medium. These results explain the variations of the intensity among the various orders noticed by Debye and Sears for variations of &#934; in a very gratifying manner

The two types of X-ray reflection in crystals

The new type of X-ray reflection forming the subject of this paper was first described and an explanation of it on the basis of the quantum theory given in a series of papers published earlier this year by Raman and Nilakantan in these Proceedings and elsewhere. The present report is intended to be a self-contained theoretical exposition of the subject and incorporates the ideas already expounded in the papers by Raman and Nilakantan, as also the fuller mathematical treatment by Raman and Nath published in these Proceedings for July 1940. Recent experiments by Nilakantan with diamond completely establish the quantum theoretical explanation of the phenomenon

GIS-MAP based Spatial Analysis of Rainfall Data of Andhra Pradesh and Telangana States Using R

The rainfall conditions across wide geographical location and varied topographic conditions of India throw challenge to researchers and scientists in predicting rainfall effectively. India is Agriculture based country and it mainly depends on rainfall. Seasons in India are divided into four, which is winter in January and February, summer is from March to May, monsoon is from June to September and post monsoon is from October to December. India is Agriculture based country and it mainly depends on rainfall. It is very difficult to develop suitable rainfall patterns from the highly volatile weather conditions. In this Paper, it is proposed that Map based Spatial Analysis of rainfall data of Andhra Pradesh and Telangana states is made using R software apart from Hybrid Machine learning techniques. A Study will be made on rainfall patterns based on spatial locations. The Visual analytics were also made for effective study using statistical methods and Data Mining Techniques. This paper also introduced Spatial mining for effective retrieval of Remote sensed Data to deal with retrieval of information from the database and presents them in the form of map using R software

Prediction of Indoor Air Quality in a School Building Using Risk Model

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv