Multi-Pass Welding Distortion Analysis Using Layered Shell Elements Based on Inherent Strain

In this article, a layered shell element-based, elastic finite element method for predicting welding distortion in multi-pass welding is developed. The welding distortion generated in each pass can be predicted by employing layer-by-layer equivalent plastic strains as thermal expansion coefficients and using the heat-affected zone (HAZ) width as the mesh size. The final distortion can be expressed as the sum of the distortions for each pass. This study focuses on extraction of the equivalent plastic strain and HAZ width through 3D thermal elastic plastic analysis (TEPA) for each pass. The input variables extracted from each pass can be converted and added to simulate the final distortion of the multi-pass welding. A 10 mm thick, multi-pass butt-welded joint, subjected to three passes, is simulated via the proposed method. The predicted welding distortion is compared with the 3D TEPA results and the measured experimental data. The outcome indicates that good agreement can be obtained.

Microstructure Evolution Mechanism of Single and Multi-pass in Laser Cladding Based on Heat Accumulation Effect for Invar Alloy

This work explores how the process parameters in laser cladding affect the evolution of the microstructure of the single pass and multi-pass cladding layers of Invar alloys. The research examined the cladding layers from three aspects: (1) the transformation of grain size, HAZ width, ratio of the columnar crystal to the equiaxed crystal, and change of Fe content of cladding layer; (2) the effects of heat accumulation on grain size, HAZ width and remelting zone; and (3) the hardness distribution of single pass and multi-pass cladding layers. The investigation has the following four findings: (1) the cladding layer is composed of equiaxed crystals at the top and columnar crystals at the bottom of cladding layer; (2) the processing parameters have significant effects on the width of the HAZ, proportion between the columnar and equiaxed crystals and the change of Fe content of cladding layer. (3) the gradual accumulation of heat causes the increase in HAZ width, the grain size, and the area of the remelting zone; and (4) the hardness progressively reduces from the top to bottom along the direction of the centerline of the cladding layer.

Parametric Influences on Heat Affected Zone in Micro-channel Milling Process of Zirconia Ceramic

Zirconia, a bio-ceramic, is widely utilized in bioengineering, biomedical implants, dentistry, and the automotive industry due to high hardness, excellent wear resistance, etc. However, it is difficult to attain micro features on zirconia utilizing a laser machining system for the aforesaid properties. The paper deals with the study of the Heat Affected Zone (HAZ) formation during the micro-channel milling (V-shaped cross-sections) of zirconia utilizing a nanosecond fiber laser system. Experiments are accomplished to examine the consequence of control variables namely transverse feed, pulse frequency, laser power, scan number, and scan speed. The influence of each of the laser process variables on response parameter are studied in order to get the significant trends of laser parameters. With the increment of laser power, the number of pass and transverse feed, HAZ width dimensions tend to increase. The reverse phenomena are observed for pulse frequency and scan speed. The lower HAZ width which is achieved as 31.74 μm at a parametric setting of average power at 10 W, pulse frequency at 65 kHz, scanning speed at 11 mm/s, a number of pass at 1, transverse feed at 0.005 mm.

A Study of Fiber Laser Micro-Grooving of 316L Stainless Steel at Different Temperatures

The present article deals with the generation of micro-grooves on 316L stainless steel (SS) by a nanosecond pulsed fiber laser system. Fabrication of micro-grooves on 316L SS has immensely contributed to the biomedical and automotive industries through improving the mechanical, lubrication, and corrosion resistance properties. In the present work, the considered process parameters are the preheating temperature (100°C and 200°C), along with the room temperature (24°C), cutting speed, sawing angle, pulse frequency, and laser power. The ranges of cutting speed and sawing angle are 0.1–1.1 mm s−1 and 0.1°–1°, respectively. Besides, pulse frequency and laser power vary from 55 kHz to 85 kHz and from 15 W to 45 W, respectively. The constant parameters are the pulse width of 99% and assist air pressure of 6 kgf cm−2. The variable parameters for the analysis are cut width and heat-affected zone (HAZ) width. The article aims to showcase a comprehensive study of fiber laser process parameters at different temperatures (preheated condition and room temperature) with variable sawing angles to produce better process control and bring about each considered process parameter’s critical value. The experimental results show that higher dimensions of cut width and HAZ width are observed at 200°C with the increment of sawing angle and laser power, compared to other temperatures. With the increment of cutting speed and laser power, the HAZ width tends to rise sharply. A significant drop in cut width and HAZ width dimensions is observed with the increment in pulse frequency for any temperature.

Effect Of Preheating On The Hardness And Microstructure In Shielded Metal Arc Weldments Of A283 B

The purpose of this study was to determine the effect of heating on the welding process of SMAW (Shielded Metal Arc Welding) in terms of hardness and microstructure of welded metal. Much welding has been done by preheating but below the temperature used below the initial martensitic temperature which reaches 452 ° C, this data is sourced from research by S.Zheng et.al and Y. Huang et.al. For this reason, an experiment was carried out with heat temperatures above a martensitic temperature of 500 ° C. The results show that in the Weld Metal area the pearlite structure appears larger, the effect of current strength on HAZ width is directly proportional, the greater the current strength, the wider HAZ, and hardness are affected by the rough grains of martensite

A Comparison Study Between Modeling The Heat Affected Zone (Haz) For The Laser Cutting Of Ti-6al-4v Sheets By Using The Artificial Neural Network Method And Multi Regression Method

This research presents an attempt to study the influence of laser cutting parameters such as thickness, Lens Focal Length, Beam Power, Cutting Speed and Gas Pressure on the Heat Affected Zone (HAZ) width. Two predictive models were developed using Artificial Neural Network (ANN) and multi regression modeling method. The relative importance of laser cutting parameters on (HAZ) width was determined based on (ANN) neuron weights and (ANOVA) method. The comparison between the experimental data and the predicted data indicats that the (ANN) model has attain an accuracy for predicting (HAZ) more than the multi regression model with a coefficient of determination of (R2)=85.02%.

Investigation on the Continuous Wave Mode and the ms Pulse Mode Fiber Laser Drilling Mechanisms of the Carbon Fiber Reinforced Composite

The near infrared (NIR) laser drilling of a carbon fiber reinforced polymer (CFRP) composite in the continuous wave (CW) mode and the ms pulse mode was investigated by an experiment and a numerical simulation. The relationships between the laser penetrating time, entrance hole diameter, surface heat affected zone (HAZ) width, and material ablation rate and the laser irradiation time and laser peak power densities were obtained from the experiment. For the same average power density of the laser output, 3.5 kW/cm2, it was found that the ms pulse laser mode, which had a higher peak power density, had a higher drilling efficiency. When drilling the same holes, the pulse laser mode, which had the highest peak power density of 49.8 kW/cm2, had the lowest drilling time of 0.23 s and had the smallest surface HAZ width of 0.54 mm. In addition, it was found that the laser penetrating time decreased sharply when the peak power density was higher than 23.4 kW/cm2. After analyzing the internal gas pressure by the numerical simulation, it was considered that a large internal gas pressure appeared, which resulted from polymer pyrolysis, causing a large amount of the mechanical erosion of the composite material to improve the drilling efficiency. Therefore, the ms pulse laser showed its potential and advantage in laser drilling the CFRP composite.