An approach to reduce stress and defects: a hybrid process of laser cladding deposition and shot peening

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiaoyu Zhang ◽  
Dichen Li ◽  
Jiale Geng
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Laser Cladding ◽  
Shot Peening ◽  
Hybrid Process ◽  
Layer By Layer ◽  
Residual Tensile Stress ◽  
Forming Process ◽  
Content Type ◽  
Thermal Forming

Purpose Laser cladding deposition is limited in industrial application by the micro-defects and residual tensile stress for the thermal forming process, leading to lower fatigue strength compared with that of the forging. The purpose of this paper is to develop an approach to reduce stress and defects. Design/methodology/approach A hybrid process of laser cladding deposition and shot peening is presented to transform surface strengthening technology to the overall strengthening technology through layer-by-layer forming and achieve enhancement. Findings The results show that the surface stress of the sample formed by the hybrid process changed from tensile stress to compressive stress, and the surface compressive stress introduced could reach more than four times the surface tensile stress of the laser cladding sample. At the same time, internal micro-defects such as pores were reduced. The porosity of the sample formed by the hybrid process was reduced by 90.12% than that of the laser cladding sample, and the surface roughness was reduced by 43.16%. Originality/value The authors believe that the hybrid process proposed in this paper can significantly expand the potential application of laser cladding deposition by solving its limitations, promoting its efficiency and applicability in practical cases.

scholarly journals Numerical Modeling Design for the Hybrid Additive Manufacturing of Laser Directed Energy Deposition and Shot Peening Forming Fe–Cr–Ni–B–Si Alloy

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4877
Author(s):  
Xiaoyu Zhang ◽  
Dichen Li ◽  
Weijun Zhu
Keyword(s):  
Temperature Field ◽  
Additive Manufacturing ◽  
Tensile Stress ◽  
Compressive Stress ◽  
Shot Peening ◽  
Energy Deposition ◽  
Hybrid Process ◽  
Forming Process ◽  
Directed Energy Deposition ◽  
Directed Energy

Hybrid additive manufacturing is of great significance to make up for the deficiency of the metal forming process; it has been one of the main trends of additive manufacturing in recent years. The hybrid process of laser directed energy deposition (laser DED) and shot peening is a new technology combining the principles of surface strengthening and additive manufacturing, whose difficulty is to reduce the interaction between the two processes. In this paper, a new model with a discrete phase and fluid–solid interaction method is established, and the location of the shot peening point in the hybrid process is optimized. The distributions of the temperature field and powder trajectory were researched and experiments were carried out with the optimized parameters to verify simulation results. It was found that the temperature field and the powder trajectory partly change, and the optimized injection point is located in the stress relaxation zone of the material. The densities and surface residual stresses of samples were improved, and the density increased by 8.83%. The surface stress changed from tensile stress to compressive stress, and the introduced compressive stress by shot peening was 2.26 times the tensile stress produced by laser directed energy deposition.

Online Stress Test and Residual Stress Analysis of Plate’s Multi-Point Plastic Forming

2009 ◽  
Vol 628-629 ◽  
pp. 575-580
Author(s):  
X.J. Feng ◽  
L.F. Liang ◽  
Yi Jun Zhou
Keyword(s):  
Compressive Stress ◽  
Stress Test ◽  
High Strength ◽  
Residual Compressive Stress ◽  
Process Conditions ◽  
Residual Tensile Stress ◽  
Forming Process ◽  
Plastic Forming ◽  
Shell Plate ◽  
Shell Forming

This paper introduces a method to measure the online strain in the plate shell forming process. It solves the problem that the inside stress online is almost impossible measured in the process of the upper and lower molds forming. The key technology is the design of the moving test frame. This frame can move with the plate’s movement to protect the sensors and ensure the output of the test signal, at the same time, it does not interfere with the shell’s process conditions. It is the first time to apply this method to the large-sized high-strength steel ball shell plate, and it could accurately measure the stress distribution and changes laws within the shell plate under certain specific condition in the process of punching to online stress test and analysis during the punching forming process. The test results show that the periphery of each pressure point is residual tensile stress, and the inside is the residual compressive stress, more evenly distributed. The existence of residual compressive stress is in favor of the anti-fatigue capacity of the plate.

Effects of Web Height-Thickness Ratio on Longitudinal Residual Stresses of the Welded Monosymmetric I-Section

2013 ◽  
Vol 671-674 ◽  
pp. 446-449
Author(s):  
Zhuang Nan Zhang ◽  
Ya Nan Zhao ◽  
Lu Jin
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Thickness Ratio ◽  
Residual Compressive Stress ◽  
Residual Tensile Stress ◽  
Stress Distributions ◽  
Distribution Width ◽  
Longitudinal Residual Stress ◽  
Increasing Trends ◽  
Peak Value

This paper descries work carried out using ANSYS finite element techniques to evaluate the longitudinal residual stress distributions of the welded monosymmetric I-section in various web height-thickness ratios. From the analysis results, it is shown that, with the web height to thickness ratio increased, the peak values of residual tensile and compressive stress in flange decrease, and the peak residual tensile stress in web decrease too, but the peak residual compressive stress increase. Meanwhile, the distribution width of residual tensile stress in flange and the distribution width of residual compressive stress in web all present increasing trends. The magnitude of the maximum longitudinal residual tensile stresses in both the flange and web reach the yield stress fy, while the maximum residual compressive stress in wide and narrow flange is close to 0.4 fy and 0.3 fy respectively, and the peak value of compressive stress in web which closes to the wide flange and to the narrow flange is about 0.4fy and 0.3fy separately. With the change of height to thickness ratio of web, the distributive width of residual tensile stress in flange or web is about 0.3 times of flange width or web height.

Fracture Mechanism of Laser Cutting With Controlled Fracture

2003 ◽  
Vol 125 (3) ◽  
pp. 519-528 ◽  
Author(s):  
Chwan-Huei Tsai ◽  
Chi-Sheng Liou
Keyword(s):  
Tensile Stress ◽  
Laser Beam ◽  
Compressive Stress ◽  
Fracture Mechanism ◽  
Laser Cutting ◽  
Laser Spot ◽  
Laser Source ◽  
Residual Tensile Stress ◽  
Finite Element Software ◽  
Controlled Fracture

Laser cutting using the controlled fracture technique has great potential to be used for the machining of brittle materials. In this technique, the applied laser energy produces a mechanical stress that causes the material to separate along the moving path of the laser beam. The material separation is similar to a crack extension and the fracture growth is controllable. The fracture mechanism of laser cutting with controlled fracture is studied in this paper. The temperature and stress distributions are obtained by using the finite element software ANSYS. The laser heat first induces compressive stress around the laser spot. After the passage of the laser beam, the compressive stress is relaxed, and then a residual tensile stress is induced, which makes the fracture grow from upper surface to lower surface of the substrate. The stable separation of the brittle material is due to the local residual tensile stress. However, if the tensile stress is distributed throughout the thickness around the crack tip, the crack will extend unstably. The experimental materials in this study are alumina ceramic and the laser source is CO2 laser. It is found that the crack propagation is non-uniform and the speed is variable during the cutting process. The relationships between laser power, cutting speed, diameter of laser spot, and specimen geometry are obtained from the experimental analysis, and the phenomena are also explained from the results of stress analysis.

Development of Stress Reduction Method in the Pipe Welded Zone

2009 ◽  
Author(s):  
Yuka Fukuda ◽  
Osamu Saito ◽  
Satoru Aoike ◽  
Fuminori Iwamatsu
Keyword(s):  
Stainless Steel ◽  
Tensile Stress ◽  
Compressive Stress ◽  
Stress Reduction ◽  
Reduction Method ◽  
Residual Tensile Stress ◽  
Low Carbon ◽  
Pipe Expansion ◽  
Inner Surface ◽  
Stainless Steel Pipe

Stress Corrosion Cracking (SCC) failures have occurred in the vicinity of austenitic stainless steel pipe welds used in boiling water reactors, since the late 70s. One of the initial countermeasures against SCC has been to use low-carbon stainless steel. However, in older plants, SCC failures in low-carbon stainless steel pipe were still observed in recent years. It is well understood that residual tensile stress due to welding largely affects occurrence and growth of SCC in low-carbon stainless steel. Because of this, it is important to reduce the residual tensile stress in the welded zone in addition to utilizing less susceptible material. However, a countermeasure to reduce residual tensile stress in small-bore pipe has not been established. In this study, a new stress reduction method is developed in order to reduce residual tensile stress in the welded zone, even for small-bore pipe. This method is applied to the butt-welded zone while the pipe is filled with water. First, the pipe is frozen at two points centering around the welded zone by cooling the outer surface of the pipe to transform the water to plugs of ice. The volume inside the pipe between the ice plugs becomes watertight and pressurized by the expansion of the plugs up-on freezing. The pipe expands near the zone of the weld groove, because the wall thickness of the butt-welded zone is thinner locally because of the weld counter bore. In this process, tensile strain occurs near the welded zone due to the pipe expansion beyond its plastic range, and then hoop tensile plastic strain of inner surface is larger than that of outer surface. Once the pressure load is removed, the difference in these tensile strains induces the hoop residual tensile stress on the inner surface to reverse to a compressive stress. On the other hand, the local bending deformation that occurs in the welded zone results in an axial residual compressive stress on inner surface. Both experimental studies and finite element analysis confirmed that the hoop and axial residual tensile stress at the inner surface of the welded zone are reversed to compressive stress by the pipe expansion.

scholarly journals Stress–strain relationship model of glulam bamboo under axial loading

2020 ◽  
Vol 29 ◽  
pp. 2633366X2095872
Author(s):  
Yang Wei ◽  
Mengqian Zhou ◽  
Kunpeng Zhao ◽  
Kang Zhao ◽  
Guofen Li
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Failure Modes ◽  
Axial Loading ◽  
Tensile Failure ◽  
Stress Strain ◽  
Laminated Bamboo ◽  
Bamboo Scrimber ◽  
Strain Relationship ◽  
Strain Model

Glulam bamboo has been preliminarily explored for use as a structural building material, and its stress–strain model under axial loading has a fundamental role in the analysis of bamboo components. To study the tension and compression behaviour of glulam bamboo, the bamboo scrimber and laminated bamboo as two kinds of typical glulam bamboo materials were tested under axial loading. Their mechanical behaviour and failure modes were investigated. The results showed that the bamboo scrimber and laminated bamboo have similar failure modes. For tensile failure, bamboo fibres were ruptured with sawtooth failure surfaces shown as brittle failure; for compression failure, the two modes of compression are buckling and compression shear failure. The stress–strain relationship curves of the bamboo scrimber and laminated bamboo are also similar. The tensile stress–strain curves showed a linear relationship, and the compressive stress–strain curves can be divided into three stages: elastic, elastoplastic and post-yield. Based on the test results, the stress–strain model was proposed for glulam bamboo, in which a linear equation was used to describe the tensile stress–strain relationship and the Richard–Abbott model was employed to model the compressive stress–strain relationship. A comparison with the experimental results shows that the predicted results are in good agreement with the experimental curves.

scholarly journals Effect of Cooling Method on Formability of Laser Cladding IN718 Alloy

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3734
Author(s):  
Jianyu Yang ◽  
Xudong Li ◽  
Fei Li ◽  
Wenxiao Wang ◽  
Zhijie Li ◽  
...  
Keyword(s):  
Laser Cladding ◽  
Primary Dendrite ◽  
Solidification Rate ◽  
Processing Condition ◽  
Layer By Layer ◽  
Water Cooling ◽  
Cooling Device ◽  
K Value ◽  
Cladding Layer ◽  
Thin Walled

The finite element model (FE) of temperature field of straight thin-walled samples in laser cladding IN718 was established, and the growth of microstructure was simulated by cellular automata (CA) method through macro-micro coupling (CA-FE). The effects of different cooling conditions on microstructure, hardness, and properties of laser-cladding layer were studied by designing cooling device. The results show that the simulation results are in good agreement with the microstructure of the cladding layer observed by the experiment. With the scanning strategy of reducing laser power layer-by-layer, the addition of water cooling device and the processing condition of 0.7 mm Z-axis lift, excellent thin-walled parts can be obtained. With the increase of cladding layers, the pool volume increases, the temperature value increases, the temperature gradient, cooling rate, solidification rate, K value gradually decrease, and eventually tend to be stable, in addition, the hardness shows a fluctuating downward trend. Under the processing conditions of layer-by-layer power reduction and water cooling device, the primary dendrite arm spacing reduced to about 8.3 μm, and the average hardness at the bottom of cladding layer increased from 260 HV to 288 HV. The yield strength and tensile strength of the tensile parts prepared under forced water cooling increased to a certain extent, while the elongation slightly decreased.

Surface integrity of quenched steel 1045 machined by CBN grinding wheel and SiC grinding wheel

2017 ◽  
Vol 8 (2) ◽  
pp. 179-187 ◽  
Author(s):  
Kankan Ji ◽  
Xingquan Zhang ◽  
Shubao Yang ◽  
Liping Shi ◽  
Shiyi Wang ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Surface Morphology ◽  
Compressive Stress ◽  
Surface Integrity ◽  
Grinding Wheel ◽  
Micro Hardness ◽  
Content Type ◽  
Quenched Steel ◽  
Cut Depth ◽  
Cbn Grinding Wheel

Purpose The purpose of this paper is to evaluate surface integrity of quenched steel 1045 ground drily by the brazed cubic boron nitride (CBN) grinding wheel and the black SiC wheel, respectively. Surface integrity, including surface roughness, sub-surface hardness, residual stresses and surface morphology, was investigated in detail, and the surface quality of samples ground by two grinding wheels was compared. Design/methodology/approach In the present work, surface integrity of quenched steel 1045 machined by the CBN grinding wheel and the SiC wheel was investigated systematically. All the specimens were machined with a single pass in the down-cutting mode of dry condition. Surface morphology of the ground specimen was observed by using OLYMPUS BX51M optical microscopy. Surface roughness of seven points was measured by using a surface roughness tester at a cut-off length of 1.8 mm and the measurement traces were perpendicular to the grinding direction. Sub-surface micro-hardness was measured by using HVS-1000 digital micro-hardness tester after the cross-section surface was polished. The residual stress was tested by using X-350A X-ray stress analyzer. Findings When the cut depth is increased from 0.01 to 0.07 mm, the steel surface machined by the CBN wheel remains clear grinding mark, lower roughness, higher micro-hardness and higher magnitude of compressive stress and fine microstructure, while the surface machined by the SiC grinding wheel becomes worse with increasing of cut depth. The value of micro-hardness decreases, and the surface roughness increases, and the surface compressive stress turns into tensile stress. Some micro-cracks and voids occur when the sample is processed by the SiC grinding wheel with cut depth 0.07 mm. Originality/value In this paper, the specimens of quenched steel 1045 were machined by the CBN grinding wheel and the SiC wheel with various cutting depths. The processing quality resulted from the CBN grinding wheel is better than that resulted from the SiC grinding wheel.

Environmental tests of embedded thin- and thick-film resistors in comparison to chip resistors

Circuit World ◽  
2014 ◽  
Vol 40 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Wojciech Steplewski ◽  
Andrzej Dziedzic ◽  
Janusz Borecki ◽  
Grazyna Koziol ◽  
Tomasz Serzysko
Keyword(s):  
Thin Film ◽  
Thick Film ◽  
Electrical Resistance ◽  
Printed Circuit Boards ◽  
Base Material ◽  
Forming Process ◽  
Content Type ◽  
Thin Film Resistors ◽  
Embedded Resistors ◽  
The Impact

Purpose – The purpose of this paper is to investigate the influence of parameters of embedded resistive elements manufacturing process as well as the influence of environmental factors on their electrical resistance. The investigations were made in comparison to the similar constructions of discrete chip resistors assembled to standard printed circuit boards (PCBs). Design/methodology/approach – The investigations were based on the thin-film resistors made of NiP alloy, thick-film resistors made of carbon or carbon-silver inks as well as chip resistors in 0402 and 0603 packages. The polymer thick-film resistive films were screen-printed on the several types finishing materials of contact terminations such as copper, silver, and gold. To determine the sensitivity of embedded resistors versus standard assembled chip resistors on environmental exposure, the climatic chamber was used. The measurements of resistance were carried out periodically during the tests, and after the exposure cycles. Findings – The results show that the change of electrical resistance of embedded resistors, in dependence of construction and base material, is different and mainly not exceed the range of 3 per cent. The achieved results in reference to thin-film resistors are comparable with results for standard chip resistors. However, the results that were obtained for thick-film resistors with Ag and Ni/Au contacts are similar. It was not found the big differences between resistors with and without conformal coating. Research limitations/implications – The studies show that embedded resistors can be used interchangeably with chip resistors. It allows to save the area on the surface of PCB, occupied by these passive elements, for assembly of active elements (ICs) and thus enable to miniaturization of electronic devices. But embedding of passive elements into PCB requires to tackle the effect of each forming process steps on the operational properties. Originality/value – The technique of passive elements embedding into PCB is generally known; however, there are no detailed reports on the impact of individual process steps and environmental conditions on the stability of their electrical resistance. The studies allow to understand the importance of each factor process and the mechanisms of operational properties changes depending on the used materials.

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