Search

Abstract: Electrical Discharge Machining (EDM) has emerged as an outstanding approach for cutting conductive metals that are otherwise difficult or impossible to be cut with traditional machining [1]. Moreover, a survey of literature has found that a little of work was carried out in the direction of achieving optimal levels of machining parameters for the super alloy Inconel 718, among other super alloys, which are otherwise difficult to machine. The objective of the present work was to investigate the effects of various EDM input parameters as well as the influence of different tool geometry on Material Removal Rate(MRR), Tool Wear Rate(TWR) and Surface Roughness(SR) on machining of Inconel 718 material by using copper electrode. Five EDM parameters, namely pulse on time (TON), pulse off time (TOFF), peak current (A), flushing pressure (P) and electrode tool geometry (Geo), were considered here. Tool geometry of the electrodes was circle (C), square (S), rectangle (R) and triangle (T). Four different levels for the five input parameters were planned as per the L16 orthogonal array. The parameters were optimized using multi-objective optimization technique of desirability approach and the significance of each parameter was analyzed by Analysis Of Variance (ANOVA). In addition, Fuzzy Logic Model (FLM) was used to better understand the input and output responses. With the desirability approach, it was sought to optimize the values for copper electrode for maximum MRR and minimum TWR and SR. Overall, the rectangular tool geometry emerged successful. A comparison of the performances of the electrode by desirability approach and ANOVA showed that the current was the most influencing factor, followed by pulse on time and pulse off time. It was also observed that the rectangular tool geometry provided better results as compared to other tool geometries. Validation tests for FLM were carried out and show closer relationship with the experimental results. [Copyright &y& Elsevier]

Abstract: Tool life prediction and tool change strategies are now based on most conservative estimates of tool life from past tool wear data. Hence usually tools are underutilized. In an unmanned factory, this has the effect of increased frequency of the tool changes and therefore increased cost. An ultrasound online monitoring of crater wear of the uncoated carbide insert during the turning operation is presented. The method relies on inducing ultrasound waves in the tool, which are reflected by side flank surface. The amount of reflected energy is correlated with crater wear depth. Various ultrasonic parameters are considered for defining the crater wear and individual contribution of each parameter is analyzed. The ultrasonic parameters, amplitude, pulse width and root mean square (RMS) of the signal are used to quantify the crater depth and width. The power spectrum analysis of received signals shows the importance of frequency components in defining the tool wear. In the presented work, the normalizing of signals are carried out by insert hole, which is provided for clamping. This signal is not influenced by the wear but affected by other factors like tool material variation, improper couplant, temperature, etc. The response of the wear signal is normalized to the response of hole signal by mathematical division. A new approach adaptive neuro-fuzzy inference system (ANFIS) for monitoring of crater in carbide insert is presented. This improves the system accuracy and eliminates the limitation in statistical modeling that was presented in previous studies. [Copyright &y& Elsevier]

The relationship between spine SBRT outcomes and the extent of malignant epidural disease (MED) compression of the cauda equina has yet to be reported. Our objective was to determine clinical, anatomic and dosimetric predictive factors for local failure (LF) and overall survival (OS) in a cohort of patients with spine metastases and epidural disease at the level of the cauda equina. Consecutive patients with cauda equina MED treated with SBRT, between January 1, 2008 and July 1, 2023, were identified and retrospectively reviewed from a prospectively maintained institutional database. MED parameters including linear dimensions, surface area, and volume ratios relative to the spinal canal, lumbar stenosis grading systems, clock position and various dosimetric factors were analyzed for their predictive value for LF post-SBRT and OS. Covariates with a P value ≤ 0.20 on univariate analysis were selected for multivariable analysis (MVA), and those statistically significant (P <0.05) were included in the final model. Ninety-five individual spinal segments (79 patients) with cauda equina MED were identified, of which 69 (73%) were intact and 26 (27%) post-op. Forty-one (43.2%) received 24 Gy in 2 fractions (fr), 27 (28.4%) received 30 Gy in 4 fr, 22 (23.2%) received 28 Gy in 2 fr and 5 (5.2%) received 30 Gy in 5 fr. Median follow-up and median time to LF were 16.3 (IQR 6.7-32.0) months and 4.7 (IQR 2.2-12.1) months, respectively. The cumulative incidence of LF at 6, 12, and 24 months was 12.7%, 12.7% and 17.4% respectively. OS at 6, 12, and 24 months was 79.6%, 58.4% and 40.7% respectively. In the intact cohort only (69/95), factors predictive of a higher risk of LF on MVA were chemotherapy naive (HR = 8.197, 95% CI = 2.198-30.303, P = 0.0017), MED greater than one third of the circumference of the spinal canal (HR = 9.632, 95% CI = 1.863-49.806, P = 0.0069), and lower V50Gy Equivalent Dose in 2Gy Fractions (EQD2) to the MED volume (HR = 1.049, 95% CI = 1.018-1.081, P = 0.0014). These factors retained significance on MVA for LF when combined with the post-op (26/95) cohort (P = 0.0047, 0.0272, 0.0024, respectively). In the intact cohort only, MVA identified oligometastatic disease (HR = 0.381, 95% CI = 0.190-0.764, P = 0.0065) and MED limited to a single spinal level (HR = 0.405, 95% CI = 0.182-0.902, P = 0.0269) as prognostic for OS. Oligometastatic disease and MED limited to a single spinal level also retained significance as predictors for OS on MVA when combined with the post-op (26/95) cohort (P <0.0001, 0.0182, respectively). We identified chemotherapy naive, MED encompassing more than one third of the circumference of the spinal canal, and lower V50Gy EQD2 to the epidural disease volume, as novel predictive factors for higher LF post-SBRT for MED at the cauda equina. Consideration for more aggressive management with decompressive surgery in those with MED spanning greater than a third of the spinal canal circumference and dose escalation to the thecal sac organ-at-risk may improve outcomes. [ABSTRACT FROM AUTHOR]

The most common complication following spine stereotactic body radiotherapy (SBRT) is vertebral compression fracture (VCF). The purpose of this analyses was to determine if predictors of VCF vary according to presence or absence of a pre-existing (baseline) VCF. A retrospective review of a prospectively maintained institutional database of patients treated with SBRT for spinal metastases performed. The primary outcome was VCF. Clinical, dosimetric and radiographic factors were reported with descriptive statistics. The cumulative incidence of VCF was estimated using a competing risk analysis method. The impact of covariates was estimated with Cox proportional hazards model and hazard ratios (HR) generated. From 2008 – 2022, 744 patients with 1813 spinal segments were treated with spine SBRT. The median age was 64.9 years, and 19.1% had a baseline VCF. The majority of segments were treated with 24Gy (42.8%) or 28Gy (27.4%) in 2 fractions, the median dose-per fraction was 12Gy (range = 5-24), 68% were de novo (no prior radiation exposure) and 235 (13.0%) had prior surgical stabilization. 254 VCF event were observed (14%), 179 were iatrogenic and 75 associated with concurrent tumor progression. The 1-, 2- and 5-year VCF rates were 8.3%, 12%, and 15.2%, respectively. 85/254 (33.5%) occurred in those with a baseline VCF and 169/254 (66.5%) in those without. On multivariable analysis (MVA), tumor progression (HR = 2.24, 95% CI = 1.66-3.04, P <0.01), baseline VCF (HR = 1.91, 95% CI = 1.35-2.71, P <0.01), mechanical pain (HR = 2.01, 1.31-3.08, P <0.01), increasing age (HR = 1.015, 95% CI = 1.002-1.03, P <0.02), fewer consecutive segments treated (HR = 0.80, 95% CI = 0.65-0.98, P <0.03), increasing dose to 90% (D90) of the clinical target volume (CTV) as equivalent dose in 2-Gy fractions (EQD2) (CTV D90 EQD2, HR = 1.007, 95% CI = 1.002-1.01, P <0.02) predicted for VCF. Predictors common to segments treated with or without a baseline VCF included concurrent tumor progression and an increasing CTVD90 EQD2. No prior stabilization surgery, involvement of the posterior elements, fewer consecutive segments treated were unique to the baseline VCF cohort, while histology, mechanical pain and higher dose per fraction were unique predictors in the no prior VCF cohort. We report predictive factors for VCF following spine SBRT and observe distinct risk factors according to presence or absence of a baseline VCF that can guide treatment decisions. [ABSTRACT FROM AUTHOR]

Diffusion-weighted imaging (DWI) enables in vivo diffusivity measurement through the ADC. Aggressive hypercellular tumors exhibit restricted water diffusion and low-ADC values. We hypothesized that areas of glioblastoma that have a high likelihood of recurrence would exhibit smaller ADC change during concurrent CRT than those areas responsive to treatment. Our study aims to compare ADC changes within the areas of the gross tumor volume (GTV) that developed recurrence versus those that remained recurrence-free. We reviewed a prospectively collected cohort of patients with glioblastoma imaged between Dec 2017 and Apr 2021 with DWI at planning (Fx0), fraction 10 (Fx10), fraction 20 (Fx20), and 1 month after a standard 6-week course of concurrent CRT (P1M). The GTV was contoured at all time points and included the surgical cavity and any residual enhancing tumor. The contrast-enhancing recurrence was contoured at the first magnetic resonance imaging (MR) timepoint showing progression per RANO 2.0 criteria. The intersection of the GTV and the recurrence volume was labelled resistant-GTV (R-GTV), while the GTV that did not intersect with the recurrence was labelled sensitive-GTV (S-GTV). Patients who did not experience failure within the GTV and had a minimum follow-up of 36 months were included in the analysis, and the entire GTV was labelled S-GTV. The interior of the surgical cavity was contoured at each time point and excluded from measurement of ADC values to avoid bias. Absolute ADC values and ADC changes (%) at each time point relative to Fx0 were compared between R-GTV and S-GTV using one-sided Wilcoxon rank-sum tests. Temporal changes were assessed using a linear mixed-effects model (fixed effects: region, time; random effects: subject). A total of 51 patients were included (median age 56y, range 20-69). The median absolute ADC values for R-GTV and S-GTV were 0.91 (IQR = 0.84-1.08) vs 0.94 (IQR = 0.87-1.10) at Fx0 (P = 0.358), 1.02 (IQR = 0.88-1.18) vs 1.17 (IQR = 0.96-1.35) at Fx10 (P = 0.011), 1.09 (IQR = 0.95-1.22) vs 1.16 (IQR = 1.00-1.44) at Fx20 (P = 0.058), and 1.19 (IQR = 1.07-1.33) vs 1.37 (IQR = 1.17-1.52) at P1M (P = 0.008), respectively. The median relative ADC change for R-GTV and S-GTV was 0.9% (IQR = -2.3-20.4) vs 15.3% (IQR = 7.5-28.5) at Fx10 (P = 0.006), 11.2% (IQR = 2.7-27.4) vs 23.1% (IQR = 11.8-27.8) at Fx20 (P = 0.048), and 22.5% (IQR = 10.1-39.0) vs 33.3% (IQR = 21.1-50.2) at P1M (P = 0.034), respectively. The linear mixed-effects model revealed a significant difference in relative ADC changes between R-GTV and S-GTV (P <0.001). Early ADC change during CRT is an imaging biomarker for treatment response and recurrence prediction in glioblastoma. Regions exhibiting smaller ADC changes during CRT indicate potential sites of recurrence, suggesting utility for MR-guided biologically adapted radiation clinical trials. [ABSTRACT FROM AUTHOR]

The most common complication following spine stereotactic body radiotherapy (SBRT) is vertebral compression fracture (VCF). Iatrogenic VCF has been widely reported, but it has not yet been reported in the context of tumor progression. We hypothesized that predictors of VCF vary with cause, whether iatrogenic or in conjunction with local failure. A prospectively maintained institutional database of patients treated with SBRT for spinal metastases was retrospectively reviewed. The primary outcome was VCF, with or without local failure. Clinical, dosimetric and radiographic factors were reported with descriptive statistics. The cumulative incidence of iatrogenic VCF and VCF with tumor progression was estimated using a competing risk analysis method. The impact of covariates was estimated with Cox proportional hazards model and hazard ratios (HR) generated. From 2008 – 2022, 744 patients with 1813 spinal segments were treated with spine SBRT. The median age was 64.9 years and median follow up was 19.9 months. Of the 254 VCF events (14%), 179 (70.5%) were iatrogenic and 75 (29.5%) associated with concurrent tumor progression. Median time to iatrogenic VCF was 10.1 months and 9.0 months in those with tumor progression. The majority of segments that had an iatrogenic VCF or with tumor progression were treated with 24Gy in 2 fractions (41.8% and 41.3%, respectively) and the median dose per fraction was 12Gy in both (range = 5-24). The 1- and 2-year iatrogenic VCF rates were 6.8% and 9.9%, respectively, and 15.6% and 22.0% in those concurrent with tumor progression, respectively. On multivariable analysis (MVA), spinal level and increasing dose to 90% (D90) of the clinical target volume (CTV) as equivalent dose in 2-Gy fractions (EQD2) were the only predictors common to both iatrogenic VCF and those secondary to tumor progression. Risk factors that uniquely increased the risk of iatrogenic VCF were presence of a baseline VCF (HR = 1.85, 95% CI = 1.25-2.74, P = 0.002), increasing consecutive segments treated (HR = 0.76, 95% CI = 0.64-0.90, P <0.01), and older age (HR = 1.02, 95% CI = 1.002-1.03, P = 0.03). Meanwhile, epidural disease (HR = 2.84, 95% CI = 1.68-4.79, P <0.001), mechanical pain (HR = 3.33, 95% CI = 1.53-7.25, P <0.01) and fewer SBRT fractions (HR = 0.65, 95% CI = 0.45-0.93, P <0.02) were predictive of VCF in those concurrent with tumor recurrence. This first report of predictive factors for VCF following spine SBRT, according to an iatrogenic cause or concurrent with tumor progression, may improve clinical decision making in VCF management. [ABSTRACT FROM AUTHOR]

• Realized a monitoring system for runout in drilling. • A novel vibration and force measurement approach is used. • Identified runout sensitive features of vibration and force signals. • A LS-SVM model is developed for runout prediction with greater accuracy. • Timely prediction of runout will improve dimensional accuracy of component. Runout is a critical problem in drilling processes, which affects tool life, geometrical tolerances and also results in increased machining cost. Runout is out of balance of the drill that causes higher vibrations at rotational frequencies and lower cutting forces in the axial direction. The objective of this study is to predict and classify the state of runout. Timely prediction of runout facilitates remedial action and improves the quality of components. A novel vibration-force based multisensory approach with LS-SVM classifier for runout monitoring of a Computer Numerical Control (CNC) drilling process is presented in this paper. The experimental study shows that the runout has a significant effect on the frequency components of vibration and force signals. A Fast Fourier Transform (FFT) analysis extracts features of vibration magnitude at 1x RPM and magnitude of axial force at 100 Hz that indicates the unbalance which is proportional to the severity of runout. An increase in amplitude of vibration signal accompanied by decrease in amplitude of force signal indicates the existence of runout. A Least Square Support Vector Machine (LS-SVM) classifier is used for modelling the runout and the model is able to predict the presence of runout with R2 of 0.99 and classifies the different states of runout with a prediction accuracy of 80%. [ABSTRACT FROM AUTHOR]

The morphology, crystal structure and magnetic properties of cobalt in as-sintered and deep cryogenic treated WC-25 wt % Co cemented carbide was investigated with scanning electron microscopy, X-ray diffractometer (XRD) and Hc meter. The results show that there was no significant change in the morphology and crystal structure of tungsten carbide, but cobalt has undergone an obvious change in its crystal structure. As the diffraction peaks of tungsten carbide shields the peaks of cobalt, additional investigation with as-sintered and deep cryogenic treated pure-cobalt was carried out. The peak intensity of deep cryogenic treated cobalt specimens reveals the phase transformation of cobalt which shows higher ε-Co and increased coercivity. The phase change of cobalt is substantiated by the higher wear resistance exhibited by deep cryogenic treated WC–25Co cemented carbide in pin-on-disc wear testing. [ABSTRACT FROM AUTHOR]