A.A. Garcia-Granada

A new procedure based on Sachs’ boring for measuring non-axisymmetric residual stresses

Abstract Sachs’ boring is an established technique for the measurement of axisymmetric residual stresses in cylindrical components. There are however important cases where non-axisymmetric residual stresses need to be found. In this paper a new procedure is developed to measure non-axisymmetric residual stresses. The essential feature of the new procedure is the use of a Fourier series to represent the residual stresses. The correctness of the new procedure is demonstrated using a finite element simulation where a set of non-axisymmetric residual stresses are determined. Excellent agreement is found between the predicted residual stresses and those derived using a finite element simulation of the new procedure.

A new procedure based on Sachs’ boring for measuring non-axisymmetric residual stresses: experimental application

Abstract A new procedure has been developed based on Sachs’ boring to measure non-axisymmetric residual stresses in cylindrical components. The new procedure uses a Fourier series to represent the residual stresses. This paper describes an experimental application of the procedure to measure the residual stresses around a hole in a specimen subjected to a uniaxial overload. Good agreement is found between the measured residual stresses and those predicted using a finite element simulation.

Engineered arterial models to correlate blood flow to tissue biological response

This paper reviews how biomedical engineers, in collaboration with physicians, biologists, chemists, physicists, and mathematicians, have developed models to explain how the impact of vascular interventions on blood flow predicts subsequent vascular repair. These models have become increasingly sophisticated and precise, propelling us toward optimization of cardiovascular therapeutics in general and personalizing treatments for patients with cardiovascular disease.

A methodology for damping measurement of engineering materials: application to a structure under bending and torsion loading.

A new method to calculate damping properties of rigid materials to be used in Finite Elements calculations is presented. Its relevance relies in its simplicity regarding the amount of materials data, mathematical treatment and experimental equipment needed. Its application allows more realistic calculation of mechanical parts and structures under dynamic loading. In most of those calculations very unreal assumptions are done when simulating with Finite Elements software to assure stability of the solution. The main reason for that situation is the lack of information of damping properties of materials in databases and the complexity of the reported methodology to calculate or measure them. Another reason is the common development time for new products in industry encouraging engineers to quickly evaluate mechanical performance of the product. Recommendations to select initial parameters are presented. Critical parameters to achieve good mathematical fits of the experimental data are identified. Theoretical treatment, fitting algorithm and experimental procedure are described and proved. Several materials: plastics and ferrous and nonferrous metals are studied to demonstrate the validity of the proposed method. Finally, the method is proved in a complex hyperstatic three-dimensional structure under dynamic loading; including working under resonance conditions. Results obtained prove the validity of the method and its application to real world situations.

Ball-burnishing effect on deep residual stress on AISI 1038 and AA2017-T4

ABSTRACT Ball-burnishing induces compressive residual stresses on treated materials by the effect of plastic deformation. The result is an increase in the fatigue life of the treated part, retarding the initiation of cracks on the surface. Compressive residual stresses have been previously measured by X-ray diffraction near the surface, revealing considerably high values at the maximum analyzed depth, in relation to other finishing processes such as shot peening. However, the maximum analyzed depth is very limited by using this technique. In this paper, the incremental hole drilling (IHD) technique is tested to measure residual stresses, being able to reach a 2-mm measuring depth. To that objective, a commercial strain gage is used and calibrated using finite element model simulations. A second Finite Element Model based on material removal rate is developed to obtain the equations to calculate the strain release through IHD. Finally, residual stresses are measured experimentally with that technique on two different materials, confirming that ball-burnishing increases the compressive residual stresses in layers up to 0.5 mm deep for the testing conditions, which is a good response to industrial needs. The method proves to be suitable, simple and inexpensive way to measure the value of these tensions.

Experimental Measurements of Non-Axisymmetric Residual Stresses

The conventional Sachs method and a new method using Fourier analysis are employed to measure non-axisymmetric residual stresses. Two examples of non-axisymmetric residual stresses are presented. The first is a highly non-axisymmetric residual stress distribution around a plain hole exposed to creep conditions. The second example deals with residual stresses arising in a cold expanded hole. The two residual stress measurement techniques rely on strain measurements in hoop and/or axial directions at a given radial distance. The Sachs method assumes that the residual stresses are symmetric, and consequently only one strain gauge is needed. However, for the new method the strain distribution at several angles is required. The angular strain measured, as a result of boring out the hole, for both examples were found to exhibit significant variations. The calculated residual stresses from both techniques are discussed and compared. The error introduced using Sachs method depends on the angular variation of the residual stresses. Not only can the conventional Sachs technique give erroneous residual stress magnitudes, but can also provide residual stresses of the opposite sign. The new method is shown to provide accurate results.