A Numerical and Experimental Assessment of the Small Punch Creep Test for 316L(N) Stainless Steels

This paper presents a finite element analysis of the small punch creep test for 316L(N), which is compared with experimental data for 650 and 700 °C. Special emphasis is placed on (i) assessing the influence of friction and (ii) comparing two different creep models: the simple Norton creep and the more general creep model. The computed normalized deflection rate versus time is almost identical for all cases, which allows for scaling of the results. The computed time to rupture increases linearly with the friction coefficient due to a reduction in the mean stress. There is a good overall agreement between the experimental values and the computed deflection rate for a friction coefficient of around 0.3. It is shown that the initial reduction in deflection rate is due to stress relaxation and homogenization, and is only marginally affected by primary creep hardening. The computed results are compared with the equivalent stress and strain rates in the recently published small punch standard (EN 10371). The computed von Mises stresses at minimum deflection decrease linearly with the friction coefficient but are consistently slightly higher than the equivalent stress in the standard. For the strain rates, the computed values are significantly higher than the equivalent values in the standard. The presented simulations give a deeper insight of the small punch creep and impact of key parameters such the friction coefficient and in general as a guidance to refinement and improvement of the empirically based formulae in the standard.

‘Mouse’ loop – for frictionless mechanics

Frictionless mechanics for extraction space closure is one of the commonly used method in orthodontic practice. The ‘Mouse” loop is a new design for efficient and low friction space closure. The 'Mouse' loop has biomechanical advantages of increased range of activation and low load deflection rate. A case report is presented for the application of the loop. In the case report, a deciduous canine was extracted and its space was closed with the help of the 'Mouse' loop. The space of the deciduous canine was closed within five months without any clinical disadvantage.

Process Window for Electron Beam Melting of 316LN Stainless Steel

Electron beam melting (EBM) is currently hampered by the low number of materials available for processing. This work presents an experimental study of process parameter development related to EBM processing of stainless steel alloy 316LN. Area energy (AE) input and beam deflection rate were varied to produce a wide array of samples in order to determine which combination of process parameters produced dense (>99%) material. Both microstructure and tensile properties were studied. The aim was to determine a process window which results in dense material. The range of AE which produced dense materials was found to be wider for 316LN than for many other reported materials, especially at lower beam deflection rates. Tensile and microstructural analysis showed that increasing the beam deflection rate, and consequently lowering the AE, resulted in material with a smaller grain size, lower ductility, lower yield strength, and a narrower window for producing material that is neither porous nor swelling.

Behaviour of One-Way Reinforcement Concrete Cantilever Slabs with Circle Openings

Sometimes there is in need to make openings in the slabs, and this greatly effects on the strength of the structural element. Therefore, this research studies the behaviour of one-way reinforcement concrete cantilever slabs and the extent of their effect and resistance. The number of openings, their location and sizes are the main parameters that have been studied. A comparison was made between four slabs with openings and a fifth reference model (solid slab). After conducting laboratory tests, differences were found in their behaviour and resistance. The decrease in the ultimate load reached 31.5%, while the deflection rate was a decrease between 3.2% and 62.7%. It was also found that the location and number of openings affected the behaviour of the slab.

Comparative Evaluation of Dimensional Accuracy, Surface Characteristics, and Load Deflection Attributes of 0.019" × 0.025" Stainless Steel Wires Sourced from Six Different Commercial Houses: An In Vitro Study

Aims & Objectives: The aim of the study was to evaluate and compare dimensional accuracy, surface characteristics and load deflection attributes of SS wires sourced from six different commercial houses. Materials & Methods: 0.019” x 0.025” SS wire samples were divided into 6 groups and evaluated and compared for the aforementioned properties. Dimensional accuracy, surface roughness, frictional resistance, load deflection rate and ultimate tensile strength were evaluated and compared. Results: Dimensional accuracy did not vary significantly. Surface Profilometry proved 3M Unitek (Group 1) to be the wire with least irregularities. According to SEM, Modern Orthodontics (Group 6) and 3M Unitek (Group 1) in terms of ‘Sa’ and ‘Sq’ respectively had the smoothest surface finish. SS wires sourced from G&H Orthodontics (Group 2) exhibited least frictional resistance. Load deflection rates varied for all the groups for all three parameters under the study. UTS was best for SS wires sourced from Rabbit Force Orthodontics (Group 5). Conclusion: No wire from a single commercial house excels in all the parameters that were evaluated, each one having its aces and minuses.

Comparative Evaluation of the Force and Load Deflection Rate for Different Loop Springs with Varying Designs, Wire Dimensions, and Materials: A Finite Element Method Study

Objective: To evaluate and compare the force and load deflection rate generated by differing unit displacement through 1 to 4 mm of springs that vary in design (Double Delta Closing Loop, Double Vertical T Crossed Closing Loop, Double Vertical Helical Closing Loop and Ricketts Maxillary Retractor), constituting wire materials (stainless steel and beta titanium), and wire dimensions (0.017" × 0.025" and 0.019" × 0.025"). Materials and methods: Computer-assisted design (CAD) model of the said loop springs was created and converted to the finite element method (FEM). The boundary conditions assigned were restraining anterior segment of the loops in all the 3 axes and displacement of the posterior segment progressively only along the x-axis in increments of 1, 2, 3, and 4 mm. Force and load deflection rate were calculated for each incremental displacement. Results: For all loop designs, force and load deflection rate increased with incremental displacement. Loop springs of beta titanium and 0.017" × 0.025" dimension showed lesser force and load deflection rate than those of stainless steel and 0.019" × 0.025", respectively. Ricketts Maxillary Retractor showed the least force and load deflection rate. Comparable force and load deflection values were found for 0.017" × 0.025" Double Vertical T Crossed Loop and 0.019" × 0.025" Double Vertical Helical Closing Loop. Conclusions: Variations in wire dimensions, materials, and designs have a profound effect on force and load deflection rate of the different loop springs studied.

Behavior of bearing reinforced concrete panels in the process of combined action

This research of has important significance in the constructive solution, manufacturing technology and labour costs. The irreversible changes in mechanical properties occur in reinforced concrete elements, decrease in compressive and tensile strength, additional deflections. In this paper, the goal was to assess the behavior of the bearing reinforced concrete panels with a combined action (fire and force) as close as possible to the actual effect in a fire. It was necessary to solve the following tasks: to determine the dependence of deflection and deflection rate on the heating of the plate and the load acting on the panel, to determine the amount of concrete falling before breaking the integrity of the panel (the formation of through cracks, determine the degree of heating of the panel from the duration of fire and force.