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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 75
PROCEEDINGS OF THE SIXTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and Z. Bittnar
Paper 63
Notch Concentrations under Combined Tension-Compression D.W.A. Rees, H. Bahai and S. Taylor
Department of Systems Engineering, Brunel University, Uxbridge, Middlesex, United Kingdom Full Bibliographic Reference for this paper
D.W.A. Rees, H. Bahai, S. Taylor, "Notch Concentrations under Combined Tension-Compression", in B.H.V. Topping, Z. Bittnar, (Editors), "Proceedings of the Sixth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 63, 2002. doi:10.4203/ccp.75.63
Keywords: notch stress concentration, photo-elasticity, finite elements, vertical slots, horizontal slots.
Summary
The photo-elastic method has been employed to determine stress concentrations
(SC) in notched plates subjected to in-plane tension combined with compression.
Validation and interpretation of the fringe pattern exploits the known solution to the
stress raiser in a small circular hole in equi-biaxial tension. These results also
compare well with an FE prediction. This has enabled SC's to be determined
experimentally for a biaxial stress ratio
![]() It is well known that small holes and slots raise the stress in loaded plates locally by factors of 3 or 4. Clearly this becomes important to an assessment of fatigue life when, in regions of high stress, cyclic loading accelerates the crack initiation process. The various design rules [2] require the SC to be known but often estimate are made for unusual geometries. The problem of crack initiation from holes and slots is an issue of safety in many loaded structures. The prediction of life is possible when the stress raiser is quantified with a stress intensity factor. The finite element technique has been used [3,4] to estimated stress concentration factors in various engineering components where fatigue cracks occur due to the presence of stress concentrations. Holes and slots are less severe than pre-existing cracks but are invariably present in most designs [5,6] appearing with fittings, connections and attachments. Here we shall examine their influence experimentally by the photo- elastic method. Firstly, this method is verified by two alternative methods (i) using the known solution to the stress concentration around a hole in a bi-axially stressed plate and (ii) from a numerical FE simulation. Thereafter, a slot is arranged parallel to the two perpendicular stress axes in turn to establish the severity of its concentration experimentally. Results provide contours of maximum shear stress in the surrounding material. These are separated into major and minor principal stresses along axes of symmetry and around the notch boundary. The degree of concentration is revealed from locating points of maximum tension and compression around the notch boundary.
Holes and slots This study shows that photo-elasticity remains a useful experimental technique for providing a full stress field around notches subjected to bi-axial loadings. The technique may be used to validate FE predictions having it self been validated from known classical elasticity solutions. When slots are aligned with applied stress axes their straight boundaries distribute tangential stress uniformly in tension and compression. A maximum concentration in stress usually occurs within the end radius, their precise position depending upon the slot orientation. References
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