Evaluating Uncertainty in Residual Stress Measured Using the Deep‐Hole Drilling Technique

Abstract: The deep hole drilling (DHD) method measures the through‐thickness distribution of residual stress in a component. Sources of uncertainty in the application of the method are identified and three different methods for determining the magnitudes of uncertainty are presented. The analyses are applied to experimental measurements of stress in two calibration studies for ferritic steel and an aluminium alloy. Finally, the residual stresses measured in a repair welded steel pipe are examined to assess the level of uncertainty.     

Advances in analysis of total uncertainties in a semi‐invasive residual stress measurement method

The ability to characterise residual stress distribution accurately and over different length scales, particularly deep into an engineering part, plays a significant role in assessing structural integrity. Two most commonly used techniques to measure residual stress fields deep into engineering components include neutron diffraction (ND) and deep‐hole drilling (DHD). As the measurements depend on several physical quantities, they are susceptible to error. The error or uncertainties may turn substantial and compromise the suitability of the results. Although noninvasive, the neutron diffraction technique is neither readily available nor portable and is limited to approximately 60‐mm‐thick specimen; errors associated with results become unacceptable at greater flight paths. Moreover, a mock‐up representing the engineering component is normally used in the ND technique. In contrast, the DHD technique is portable and measures residual stresses with high spatial resolution. An error propagation technique was applied to develop an error analysis procedure taking into consideration various stages of the DHD method and successfully applied to different DHD measurements. An essential feature comprising the effect of plasticity due to the creation of reference hole in the DHD procedure has not yet been taken into account in the error analysis procedure. This paper briefly describes how the uncertainties due to the creation of the initial reference hole can be determined. The effect of plasticity in the drilling procedure is quantified in this study. This error is combined with other sources of error and formulated to determine the total error. An incremental DHD technique was used to measure the complex triaxial residual stress field in an as‐welded circular disc, and the measured data were used to illustrate the total error using the error analysis method developed in the study.     

Effect of Tin on the Wear Properties of Spray Formed Al–17Si Alloy

In the present study, the effect of Sn on the dry sliding wear behavior of spray formed and hot pressed Al–17Si alloy as a function of applied load and sliding speed has been investigated and compared with that of as-cast alloy. The microstructure of spray formed Al–17Si alloy consists of fine and uniformly distributed Si particles and that of Al–17Si–10Sn alloy consists of fine and uniform dispersion of Si particles and ultra-fine Sn particles in α-Al matrix. Coarse and segregated microstructures were observed in as-cast alloys. The wear resistance of spray formed alloys is higher than that of as-cast alloys. The wear resistance of as-cast Al–17Si–10Sn alloy is higher than that of as-cast Al–17Si alloy. The high wear resistance of spray formed Al–17Si–10Sn alloy is discussed in the light of its microstructural features and the nature of worn-out surfaces.     

Entropy generation analysis from the time-dependent quadratic combined convective flow with multiple diffusions and nonlinear thermal radiation

Diffusions of multiple components have numerous applications such as underground water flow, pollutant movement, stratospheric warming, and food processing. Particularly, liquid hydrogen is used in the cooling process of the aeroplane. Further, liquid nitrogen can find applications in cooling equipment or electronic devices, i.e., high temperature superconducting(HTS) cables. So, herein, we have analysed the entropy generation(EG), nonlinear thermal radiation and unsteady(time-dependent) nature ...     

Turbulent Flow Friction Factor Calculation Using a Mathematically Exact Alternative to the Colebrook–White Equation

We present a novel, mathematically equivalent representation of the Colebrook–White equation to compute friction factor for turbulent flow in rough pipes. This new form is simple, no iterative calculations are necessary, and is well suited for accurate friction factor estimation. A limiting case of this equation provided friction factor estimates with a maximum absolute error of 0.029 and a maximum percentage error of 1% over a 20×500 grid of ε/D and R values (10?6 ? ε/D ? 5×10?2; 4×103相似文献   

Competitive Substrate Biodegradation during Surfactant-Enhanced Remediation

The impact of synthetic surfactants on the aqueous phase biodegradation of benzene, toluene, and p-xylene (BTpX) was studied using two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium dodecyl benzene sulfonate (SDBS), and two nonionic surfactants, POE(20) sorbitan monooleate (T-maz-80) and octylphenolpoly(ethyleneoxy) ethanol (CA-620). Batch biodegradation experiments were performed to evaluate surfactant biodegradability using two different microbial cultures. Of the four surfactants used in this study, SDS and T-maz-80 were readily degraded by a microbial consortium obtained from an activated sludge treatment system, whereas only SDS was degraded by a microbial culture that was acclimated to BTpX. Biodegradation kinetic parameters associated with SDS and T-maz-80 degradation by the activated sludge consortium were estimated using respirometric data in conjunction with a nonlinear parameter estimation technique as μmax = 0.93 h?1, Ks = 96.18 mg∕L and μmax = 0.41 h?1, Ks = 31.92 mg∕L, respectively. When both BTpX and surfactant were present in the reactor along with BTpX-acclimated microorganisms, two distinct biodegradation patterns were seen. SDS was preferentially utilized inhibiting hydrocarbon biodegradation, whereas the other three surfactants had no impact on BTpX biodegradation. None of the four surfactants were toxic to the microbial cultures used in this study. Readily biodegradable surfactants are not very effective for subsurface remediation applications as they are rapidly consumed, and also because of their potential inhibitory effects on intrinsic hydrocarbon biodegradation. This greatly increases treatment costs as surfactant recovery and reuse are adversely affected.     

Estimating growth kinetics of Penicillium chrysogenum through the use of respirometry

The applicability of respirometry to characterize fungal growth kinetics was studied using Penicillium chrysogenum as the model microorganism. Oxygen uptake data were used in conjunction with a nonlinear parameter estimation technique to determine the kinetic parameters associated with microbial growth. The theoretical model that used the Contois equation for microbial growth was able to accurately describe experimental oxygen uptake data. Penicillium chrysogenum was characterized by average values of 0·195 h⁻¹ and 4·13 for the maximum specific growth rate, μ_max, and the Contois saturation coefficient, K_c, respectively. The average true growth yield was 0·405 mg mg⁻¹. As only oxygen uptake information is required for biokinetic parameter estimation, respirometry is a very convenient tool for studying microbial growth as high quality experimental data can be obtained with relatively little experimental effort. © 1998 SCI     

Constraints for Using Lambert W Function-Based Explicit Colebrook–White Equation

We analyze the general applicability of a recent explicit expression of the Colebrook–White equation for turbulent flow friction factor calculation. This explicit expression, which is based on the Lambert W function, is characterized by an exponential term which imposes restrictions on its use. These constraints have been expressed in terms of pipe roughness (ε/D) and the Reynolds number R that are required for friction factor calculation. These constraints were determined as 8.0666?ln(R)+(ε/D)R<721.97 and 8.0666?ln(R)+(ε/D)R<5731.83, respectively, for machines using single precision and double precision computations. Using the Lambert W function, an explicit equation relating R and ε/D was derived at the limiting case which allowed for a graphical representation of the applicability of the explicit form of the Colebrook–White equation in the R versus ε/D space. Before computing friction factors using the explicit Colebrook–White equation, a quick check must be performed to see if the desired combination of R and ε/D values satisfies the applicable constraint mentioned above.